To get your map in-game you need to place a Portal (not a gate). To do this click the Has Portal in the "Map" tab. Next find where you want to arrive in the map and face the direction you want to be looking. place the pointer on that point. Look in the lower right of the screen you should see the coordinates (note: DO NOT move the pointer) write down the X,Y,Z and Yaw Numbers on a piece of paper. Then type those numbers in the coordinate boxes and SAVE the map. Exit the game completely, then restart the game, and log-in. Now you should have a portal in Cape of Distant worlds to your map.
As for making it private, Just don't give the map files to anyone. Then it will be for you alone.
Hope this helps
