After brief exposure to the the 1500 Megawatt Aperture Science Heavy Duty Super-Colliding Super Button, you reach Test Chamber 02.

Go through Portals

When you reach the glass window, you will see something rotating in the middle of the room that is creating blue portals. After a helpful message from the computer voice, the door will open. Go through and down the stairs, and if you seem trapped, just wait for a few moments. The rotating object in the part of the room that you can't reach will shoot a blue portal onto the wall in this area. When it does, go through it.

Now you are up on a ledge, and you can hop down to the area with the rotating object, or you can go through the orange portal when the rotating object creates a blue one in that area.

Get the Portal Gun

Walk up to the rotating object and you will pick it up. The computer explains that the object is a Portal Gun. It creates blue portals.

Reach the Chamber Lock

Now that you can create blue portals, create one on a nearby wall and walk through it. The chamber lock will be open now, and you can go into the elevator to the next level. Unlike most equipment in the facility, the Portal Gun is not destroyed in the Incandescent Particle Field.

The elevator takes you to Test Chamber 03.