Git > How to push (commit) a repository to a remote repository?

Git > How to push (commit) a repository to a remote repository?

I'm new to git. I'm a web designer, not a developer.
The company that I work with has installed a git repository on my desktop
at home. When I have modified the php and image files, how can I push
(commit) them back to the remote repository?
I have downloaded the Windows GetHub application... Can I do it more
easily from there than the command line?
Any ideas or comments will be appreciated.
neuhaus3000