Welcome the Guild Christian! The best place to begin is the Quickstart Guide to Fantasy Mapping. There are heaps of tutorials in the tutorials section that might also be of use. If you can find the time to mine this section it will pay dividends in your mapping future. Also, I'd recommend browsing the finished maps section as a source of inspiration. If you find any pieces that you particularly like you can always inquire from the artist directly about the techniques they used to create it.
Cheers,
-Arsheesh