Welcome, O great piemaster. Indeed, many of us do not play D&D. For some here, the map IS the play :-).
There are many tutorials you can work through to help you develop skills at many styles and scales of mapping. One initial decision point could simply be - what graphics software to you have access to, or do you want an excuse to get ? Or are you a papyrus and pen kind of person ? - not everything afoot here is digital.