To use the teleport code (the one featured in the list of console commands) you'll just have to do this:

1. Start the game and start playing on a level.

2. Press the TAB key. This key is sometimes represented as two arrows on some keyboards.

3. Enter "SET INPUT <key> TELEPORT", where <key> (with the < and the >) is replaced with the key you want to do the teleporting with.

4. Teleport away. The teleport goes to where your targeting reticule (auto-aim works for enemies, yes) is pointing, if it is pointing at either an enemy, the floor or the roof. If there is a hidden wall of any other kind of obstacle (doors doesn't work), jumping and teleporting in the air should get you past most of the time.