Hi Nikky, and welcome. Glad you've found us.

I do recommend working through a couple of tutorials (there are lots for Gimp in this comment). You'll learn many basic processes (for example, how to create coastlines) and you can use this knowledge to develop your own maps. Be warned however... mapmaking is very addictive!

Looking forward to seeing some of your work, and if you need help with anything, just holler.