Mission Editor...

[militaryman]

made my own map, added tactics and target platforms for each ship/sub/plane but i can't figure out how to choose a platform for ownship...can someone help?

[Molon Labe]

There are about 5 pages for every object that you place on the map. The things you mentioned are on the first page. You can access the other pages by clicking the arrow icon in the lower corner. On the 2nd page, there is a toggle for "controllable platform," which should be what you're looking for.