If you're using a free host, this is often a problem. If you paid for your host, you usually have access to change the template on your phpBB. If you have no idea, just e-mail your hosting company and ask them if it's ok if you change the template on your phpBB. Sometimes if you have a free host, you can ask them if they will upload the template for you.
When you signed up for your account, did you get FTP information? In order to FTP into your account, you need this kind of information: yourhost.com, port 23, username, password. If you don't have this information, e-mail your host and politely request FTP access. If they say no, then you know that you can't install a template by yourself and you can politely request that they upload the files for you. If they refuse, then your only option is to either upgrade service with this host (if they offer a level of service with FTP access) or find another host that will allow you such access.
Here is an example e-mail that you can use to request FTP access or template uploads:
To: Your Hosting Company
Subject: FTP Information Request
Hello, I am the administrator of YOUR SITE'S NAME located at (http://www.yoursite.com) with the account name YOUR ACCOUNT NAME WITH THE HOST. I am currently running a phpBB community and I would like to add another template. In order to do this, I need to have FTP access. If it is possible, would you please forward my FTP account details to me?
If it is not possible to give me FTP access, would you be willing to upload a template for me? I can send you the files or I can send you the link to a site where you can download it.
I feel that having a unique look on my community is crucial for its identity and I selected this template so that I can attract users to my forums.
Please let me know as soon as possible. Thank you for your time.
Step 2. Find a template that you like.
Now you need to find a template that you want to install on your phpBB. Here are some links:
You want to have a template that is compatible with your phpBB version. If you find a template that you like, but that is not compatible with your version (this will usually mean that you are using the latest version of phpBB, but that the template is not yet compatible for that version), you can upgrade it so that it is compatible to your version by applying the code changes that have occurred between the phpBB version that it is compatible with and your version of phpBB.
Now, download the template that you like (for the demo, I chose ashHawaiian Template):
Save it or open it, either way is fine.
Extract it to a folder where you can easily find it. For example, I have a folder in my C: drive called "forums" and inside that folder, I have another folder named "themes". It's purely up to you.
Make sure it extracts the template with only one main folder. For example, you want the ashHawaiian Template to only have 1 folder name that says ashHawaiian. You don't want to see ashHawaiian/ashHawaiian/.
Now you need to upload this whole folder to your forum. On to step 3...
Step 3. Get an FTP program.
There are dozens of FTP programs out there. Some of the most popular are CuteFTP, WS_FTP and SmartFTP, but there are many, many other programs out there. Any of them will work fine for this. If you don't know where to get an FTP program, go to http://www.download.com and there is a category for FTP programs under Utilities. (Or you can just search for them.) Many are free or have a free demo or trial.
For this tutorial, I am using SmartFTP. Now, enter in your FTP information. On to step 4.
Step 4. Connect to your server and find your templates folder.
Notice how you need to enter in your host address in .com form? You can also put an IP here, such as 123.45.678.9 - just refer to your host's FTP details information or ask your host if you have problems.
Once you enter the information in your FTP program, connect to the site and you will see a bunch of folders and files. You need to find your phpBB installation.
Usually your phpBB installation is in public_html, so double click on that folder to pull up what is called your root directory. In the picture here, both of those arrows are pointing to the same folder. Most FTP folders show the folder tree (which shows where folders are located) on the left and the folder and file view (which shows folders AND files) on the right. If you double click either of those public_html folders, it will take you to the same place.
Now you're looking for your forum's folder and you want to find the templates folder within your forum directory. The subSilver Template is the default phpBB template, so it should be there already.
Step 5. Upload your new template to this folder.
Now drag the entire new template's folder to the /templates folder.
IMPORTANT: Make sure that you do NOT upload the new template folder like the top image. Notice how it is ashHawaiian/ashHawaiian? It should only be ashHawaiian, like on the bottom:
Step 6. Install the template!
Go to your phpBB (NOT FTP) and log in as the administrator. Go to the admin panel. Look for the Styles Admin section on the left side of the admin panel.
Now click on Install.
If all goes well, you should see this:
If it didn't work, try to say which steps you've already done and what error messages you got. Post your problems in the Templates and Graphics Discussion forum.
If nothing else, you can always ask someone to install it for you.
* Template is usually the same thing as skin, style and theme. It changes how your phpBB looks. Technically a style changes the colors and a template/theme changes the whole layout, design, buttons... all of that. A skin is just a generic computer term for changing the appearance of a program.