Activating the Pack-a-Punch machine is a relatively easy step.
First, one has to open enough doors to gain access to all three Matter Transference Devices (M.T.D.'s), also known as Teleporters. The following map perfectly indicates the three locations:
Now, you have to link them to the mainframe in the spawn room.
To do this, step inside an MTD and press your activation button, which will be followed by a mechanical noise and the appearance of a clock on your screen counting down from 30 seconds.
Within this time period, someone must go to the mainframe and activate the receiving pad in front of the Pack-a-Punch machine.
Do this with each MTD until the door is fully open. This will permanently allow the players access to the Pack-a-Punch machine.