I've been playing this game for some time now, and I have to say it is simply amazing. Still, I have no idea how to play the maps that I create in the editor. Alas, whenever I press "test" to try out the map in the editor itself, the game crashes. However, I can live with that. I just need someone to tell me how the hell can I play my maps in skirmish mode. Any help would be very, very appreciated. Thanks in advance.

The editor crashing is a bug. You can't test them that way.
You willhave to make a complete, full-fledged scene (yeah, it sucks, I loved creating massive bases in the editor and playing them for ours).

I've never done a scene myself, so I can't help you much. Go to the mod making section and you will find what you need to learn there.