Welcome, Yuki (that's "snow" in Japanese, you know.)
You've found the right place to learn how to create an RPG map, that's for sure. Look through the finished maps forums and search for a style of map you like. Be sure to look under the names of the forum posters, which usually show which software primarily used by that mapper. If you have access or can download the app you'd lke to experiment with, then go to the Tutorials forums and try some out. Once you start to understand the techniques involved then branch out on your own with your own style.
Make sure you post your maps here early, even you don't think they're ready. Let us critique and comment, so you can learn what works, what would be better and other techniques worth doing. Its the fastest way to learn.
Again, welcome, I hope you have fun here!