How do I get tiles on tilemap to be transparent

I have a tilemap with transparent backgrounds for the tiles, but when I try to use them (for example adding a tree tile to a grass landscape) the transparent part of my tile shows up white. Probably an easy fix but I couldn't find anything to help. Thanks for your help!

You will need two tilemaps. One for the background, and one for the overlayable objects, like trees. You can't have 2 tiles in the same spot, that's why you use two tilemaps (or more) for layering.

Thanks for your help Magistross!