How to set the nikon d3100 to 'bulb' mode?

I just got one recently, and i heard you can use bulb mode to take pictures of the night sky, but i can't find it anywhere.supposively it's under ' manual ' but i still can't find it. Any help?

Added (1). Okay but for that, is the manual mode the 'M'?
And where do you go to adjust the shutter speed when you're at the 'M' on the wheel?

The first guy is right. It doesn't have a separate bulb mode.
But if you go to manual and go past 30 seconds it will show bulb.

Yes, set it to Manual Mode.

Then, changing the shutter speed, scroll down till you see 30" and then scroll down one more.

This way, the shutter will stay open for as long as you hold the shutter button down.

Yes, it's the 'M' on the mode dial.

"M" mode, then turn the command dial, which is the wheel on the back of the camera near the top, under your thumb, to change the shutter speed.