The instructions below are written specifically for those accessing their site directories through cPanel. FTP user will need to adapt the instructions.
Before getting started - a note about modules
Modules available at Drupal.org are not guaranteed to work as described there, or even work at all.
It is very recommendable to read the "issues" page for any module you are considering installing to see what others are saying about the module and to be sure the version you are downloading is actually the right one for you. Sometime, unfortunately, it's not as simple as just picking the one which is "obviously labeled correctly". Some after-install tinkering is often required to get things working properly.
Finally, and above all - always make a backup before doing any work which will affect your database. If you have a backup there is virtually nothing you can do to mess things up which isn't reversible. If you don't have a backup, there's a lot you can do to make your site irreversibly messed up. :)
First goto: http://your-site-url/cpanel and login:
1. Once you're logged in navigated to the "File Manager" icon and click.
2. then click the "public_html" folder icon. Everything you put in this folder is "public", meaning that others and/or search robots will be able to "see" it.
3. locate the "modules" directory and click it, then click (or if you don't have one, make) the "CustomModules" directory within it.
4. Select the "Create New Folder" link at the top of the page and name your new folder appropriately. No uppercase and no spaces.
5. Once you've made your new directory select it's folder icon, and then after the new page loads select the "Upload file(s) link which is at the top of the page.
6. Select the files on your desktop which you want to be uploaded and upload away.
7. Go to your modules administration page at your-site/admin/modules and enable your newly uploaded module(s)
8. Configure the modules specific settings on the module settings page which you can get to by going to you admin pages at for it. (hopefully you've read the "readme.txt" files that came with your module by now)
9. Test your module's functionality by logging in as different test users.