Welcome to the Guild Belial! Well having the software and knowing how to use it means that you are already halfway there. There are tons of great map-making walk-throughs for PS in various styles in the Tutorials section, so get to know if pretty well. Also, have a look at the finished maps section and especially at the Cartographers Choice section, as you will find a lot of inspiration there. Once you begin working on a piece, throw up a WIP and you'll be sure to elicit feedback from the community. Look forward to seeing your work.