To add a portal in your map, go to map maker and view the first tab, believe it's called "Map." See where it says "Has portal" and a little box beside it? Make sure it's checked in, and then the little coordinates XYZ Yaw are stuff you'll have to add in.
To do this, place your mouse where you want the portal to be in your map and copy down the numbers in the bottom right hand corner on to a sheet of paper, and then type this into their respected boxes (They go in order, left to right is coordinated with top to bottom) The last number will be the yaw, which is the direction you're facing.
Hoperz that helped.