Map Land Types and How to

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Hi, i have just started to make maps and I think this is all pretty awesome how it is set up. With that in mind though I do not understand how to do different types of lands, because i have seen brown soil and swamp lands and i want the swamp land because it would be a nice addition to a map i am working on. I have been playing around in photoshop a bit so have somewhat of a hang on it, thanks for the help!