You need to link the two doors together. Are you following thehttp://www.youtube.com/watch?v=Y2xskfNS8HE&p=0697E09E0839D993&playnext=1&index=1, they will teach you all of these basics and get you rolling quick.
To link two Doors together:
1. Double-click one of the two doors to open it's Reference window, and pull that little window aside for a minute.
2. Load-up the cell that has the other end of the door.
3. In the Door Reference window you opened in step 1, click, "Select Reference in Render Window", which will bring up a new crosshairs.
4. Double-click on the destination door, which should spawn a yellow XMarkerHeading in front of the door. If you see this, you've got it right.
5. Click "OK" on the Door's Reference window.
6. Make sure the XMarkerHeading is facing away from the door and placed just in front of it.
7. Go back to the original cell and make sure the XMarkerHeading on that door is facing away from the door and placed just in front of it.
8. Save and Test.
Try those tutorials, they really are awesome.
Luck,
Miax