Step 1. Place Portal in Surveyor.
Step 2. Click on Portal with the tool-which-I'm-not-sure-of-the-name-of-but-the-button-looks-like-a-question-mark tool (I assure you, that is the real name)
Step 3. Set time interval. (should be fairly obvious)
Step 4. Set up consists to emit from the portal. The top of the list of cars will come out first.
Step 5. Add a driver and his or her driver commands.
Step 6. Go into driver mode and stand in amazement at your creation.
The cake is a lie.