Hey.

Are you looking for a way to upload your PHP scripts on to the server, or are you looking for a way for you PHP scripts to receive file uploads from your users?

If it is the former, you will need some sort of access to the server's hard drive. Most commonly this is done using FTP.
You should contact your host and ask them what sort of access they provide, and for your FTP login info.
Then you just use a FTP client, like FileZilla, to log in and upload your stuff.

If it is the latter. Try a Google search for "PHP file upload". You can find all the info you need to get started just on that first page of results.

As to using phpMyAdmin. What exactly are you having problems with?
It's a fairly simple application. Just mess around with it a bit before you start on the more serious work, just to get a feel for it.