1) Click the button with a key on it.
2) Select "New".
3) Choose your .SMC file.
4) Now click the button with a folder/globe on it.
5) Select an area.
6) You can change area whenever you want, but there MUST be a 
patch for that area already, or it'll just come up blank.
7) Select what door you want to set the pointer to, from the menu 
to the right.
8) Click on the map where you want to the door to lead to.

*You can place doors in the "wrong" area.  For instance, town doors 
drop you off on the ranch.
*Soon, you'll be able to have choose ANY area in the game (including 
buildings) to drop someone off in.
*Also soon, you'll be able to control where these door take you when 
you go through them in the other direction (ie- entering).