Ok, there are basically a couple of steps here.
The first is in identifying where you want to contribute. My understanding is that you are looking at contributing to the user documentation. There are two open source parts here: the manual and the book at
book.ledgersmb.org.
These are both written in LaTeX as structured documents. One nice thing about this is if you send us text you want to see changed, we can merge this in really fast. There are a few conventions that would help us out:
1. Separate paragraphs with two line spaces. This makes paragraph text something we can just copy/paste into the original document.
2. If you get to the point where you want to be involved in presentation and management of the documents as well, it might be good to get an overview of LaTeX. This is not necessary at first. I could walk you through the basics on IRC, etc. But lets start with #1 above.