As a midphase customer, you can edit any file via your cpanel web interface. (Although I prefer to use Adobe GoLive.) Log onto cpanel and then select "File Manager" under "Files". The File Manager will appear showing a crude directory tree. The files you want will all be under the "public_html" directory so click on that. This will show the files and directories in your web site. In your case, you've installed WordPress to a directory called "weblog" which you should see at this point. (You should also see the file ".htaccess" at this point for future reference.)
Once in your "weblog" directory you can browse around and eventually find just about any file mentioned in this forum or in regards to WordPress. But the main files for whatever theme you're using will be located under the "wp-content" directory, then the "themes" directory under that, then under a directory probably named after the theme you're using. (Example: wp-content\themes\classic) Once there, you'll see the main files such as "index.php", "sidebar.php", etc. that are used. (This is all good to learn any way in case you ever need to make a quick change to your web site and aren't sitting in front of your main computer.)
Clicking on a file such as "sidebar.php" brings up a menu in the top right-hand corner of the browser. If you then click on "Edit File" it will open up "sidebar.php" in a window where you can make changes and then save the file. (The WP Codex has excellent examples of how the code works and all the possible alternatives.)
If you know anything about HTML, the sidebar.php file will start to make sense. You'll see by example how to insert, copy, change things. It's not a bad idea to load a few other themes even if you don't actually use them, just to look at their code.
In the theme I downloaded from someone else, the index.php called for an image for the header. I made another the same size and saved it to the theme directory with the same name. And so with many other tweaks and amendments. The subscribe buttons and code were all supplied by a wonderful WP plugin called "Subscribe Me" that I highly recommend.
Sorry this is so long, hope this helps.