Instructions
Start the "Kino der Toten" map in "Call of Duty: Black Ops" and begin playing the game as you normally would. Open the doors and follow the passageways to get to the power room.
Turn on the power by flipping the switch up on the stage. The stage curtain will now pull away to give you another route to take. At the edge of the stage on the other side of the curtain is the transporter.
Walk into the transporter. You will be told in a pop-up message to "Initiate the Link." Do so as prompted and then follow the new route that opened back into the lobby where you started.
Stand on top of the colorful, round platform in the middle of the lobby and press the indicated button when prompted to "Complete the Link."
Walk back to the transporter on the stage and stand in the middle of it. Press the indicated button to activate it whenever you're ready. You will now be brought to a special room overlooking the theater. Inside the room is a weapon upgrade machine and grenades. After 30 seconds, you will be sent back to the middle of the lobby. When the next round starts, repeat these steps to use the transporter again.