Supose the maps are named map1 and map2. This is the "Map Name" not the "Map Display Name".
You activate the "has portal" option on both, and set the coordinates. That will be the portal to the Cape.
Next, open map1, go to objects and in gate destination write "map2" and the desired coordinates. Do then click "New Gate" and place it. Now you will have a portal with a vizible entrance in map1 and an invizible exit in map2. Do the same for map2.
If you want the portal to be 2 ways, you can simulate this by making the exit coordinates from one portal match the entry coordinates of the other.
P.S. You will not be able to actually test that the portals are working well untill the server is up.