Hello there, I've had a few minor encounters with map making in my past, although none of them were notable at all, I'm picking up the trade now cause I've been elected DM of my group, and have very little interest in using pre-made maps or worlds.
Welcome to the Guild TheEvilsoky! Many new DMs come here with exactly this need (I was among them). Check out the tutorials section, there's lot's of great info there to get you started. If you don't currently have any mapping software, download GIMP. I'ts free, fairly powerful and well supported in the tutorials section here.