ok, umm, puni,
1.you dont need starforge for melee maps
2.you cant use triggers in melee maps
3.what do you mean by story?
ok heres some pointers:
make the areas where players start even amounts of terrain, use all kinds of terrain, dont just use dirt and high dirt. in the main bases, make 7 or 8 mineral patches which have 1500 minerals in them. make a geyser which has 5000 in it.
make expansions. you know what i mean by expansions right? Make some with 5 mineral patches or some just with gas, or some with both. make expansions that need to be fought over. make doodads so people can take cover when microing. because a unit has a 75%(i think, something like that) chance of dodging. this info will be nice help for you to start off. good luck, make a few maps and post them in the melee showcase and we can help you improve them.
ADDITION:
BTW, welcome to SEN