Install GIT
On Windows, install TortoiseGIT. Just google for it, you need tortoisegit and also msysgit (tortoisegit will point you to the download).
I recommend picking "Checkout as is, commit as UNIX linefeeds" when asked.
Work with It
Clone the repository
Right-click a nice directory on your disk. Pick "Git Clone...".
Copy the GIT link from GitHub (or whatever) and paste it into the "Url" box. Hit OK.
If all's well, it creates the directory structure for you and grabs all the files.
Do your thing
Edit files, add them, move them, copy them from your box, whatever...
Commit your stuff
When you think you have something worthy, create a commit. You can do more than one, and there's also stuff to amend changes if you made a mistake. Use it!
Create a patch
If you can't push directly, just create a patch and send it to the PLi team, on the forum for example. Someone will pick it up and commit. You can continue making more changes as you see fit (just don't "amend" your commit once you sent the patch).
