Moving to the Game Help board. Be sure to pay attention to where you post your threads, floofie.
As for your portals, it sounds like you'r trying to ask how to link one of your custom maps to Cape, nu? Here's what you do:
1.) Grab a pencil and paper.
2.) Open your map in Map Maker
3.) Move your screen so it is facing the direction you want your characters to land when they spawn in the map.
4.) Next, place your mouse/cursor on the spot you want your character to actually land. Do not move the mouse from here.
5.) Don't move the mouse. o-o
6.) Then, look at the bottom left of the screen, and note the X, Y, Z, and Yaw coordinates in the box.
7.) Using that pencil and paper you had, write down each coordinate.
8.) You can move your mouse now. Now go to the main Map Maker tab (where you can save/export your map), and then check the box that says "Has portal"
9.) A dropdown of X, Y, Z, and Yaw coordinates will appear once you've checked the box. Take those coordinates you wrote down on your paper, and type them in according to their letter (X, Y, Z, and Yaw)
10.) Once you've done this, you can test whether or not your portal is there by hitting "Test" and running around in the test screen to see your portal. It should be directly behind where your character will land, like a normal portal.
11.) When you're happy with the placement, you may hit Save, and then enter your map in-game, through Cape.
Hopefully this helps ya~