https://www.coh2.org/topic/18826/help-please
this thread is where i asked a lot of questions to the community when i first started map making. you should look through and see if anything i asked also apply to you.
the community was there for me when i started from scratch. so ill be here if you want to ask more question.
one pointer though. you should use TILES the last - it is the one where you paint in textures. if you overlay more than 8, you get nasty black spots you can only delete by deleting whole tile(s).
try to populate with textures from splines and splats. you'd be amazed how good and "normal" a map looks with only one default tile and proper use of splats and splines.
AND take advantage of "atmosphere setting". when you are making maps, you probably want to turn off "fog". then your map might look bland and monotone. but with good atmosphere setting (which you can tinkle with fog levels), your map can look much better.