how to hook up phone jack?

If the home is a little more modern then it is probably wired with Cat5 cable. This has 8 cables and can be a little confusing.

Phone lines only use 2 wires per line. The wires for the main line are the red and green lines on older cables and jacks. If there's a second line like a business line, then it will usually use the yellow and black wires.

Cat5 cable uses striped wires. This adds to the confusion, but it's really quite simple. As in the picture, attach the white wire with blue stripes to the green terminal screw on the phone jack.

Attach the blue wire with white stripes to the red terminal screw on the phone jack. Plug the phone into the jack and if you did it right, there will be a dial tone.

You can get more info with photos here:

There will be colored wires coming out of the wall, and colored wires on the screw terminals inside the jack. Match the colors.
Yes, it really is that easy.
Indeed it is that easy, almost.  The only problem that can come up is if the wires found inside your walls are, for some reason, not the usual colors. 

I found the images below via a google search.

The guy in the second picture is doing it wrong.