Q: My iPad3 wifi won't pair with my new iMac blue tooth keypad. Why?

Make sure both are fully charged.

About using keyboards and headsets

http://support.apple.com/kb/HT4111

Connecting keyboard

1)  on iPad:  pull up Settings > General > Bluetooth

2)  slide from Off to On  (or On to Off, wait, then Off to On again)

3)  on keyboard:  hold down the power button on the side until the little green light flashes

4)  release

5)  on iPad:  "Apple Wireless Keyboard" should pop up under "Devices"

6)  if yes, tap "Not Connected" so it searches for a return signal from the keyboard

     if no, try resetting/restarting your iPad (holding down the Home button and the Sleep button at the same time) and repeating instructions

7)  on keyboard:  send the iPad a return signal by pressing the Shift key

Bluetooth frequently asked questions

http://support.apple.com/kb/HT3887

Bluetooth glossary of terms

http://support.apple.com/kb/HT3894