To upload a map or any kind of file on the thread you need to start a reply and look down. It will say "Add attachment". Click on it, browse the file you want to upload and that's it. If you want to upload more than one just click on the next "Add Attachment".
Hey! I like how you have added the planet in the background. This gives me ideas for my future terrain maps. Overall, it is a nice picture, but this could be done without photoshop. ( I mean in the editor)