I too am new to kegging. I'd recommend going through some of the articles in the kegging FAQ sticky (near the top of the bottling/kegging forum). I think you might be confusing volume of CO2 in your beer with the psi of the CO2 tank, not the same thing.
There are several methods to carbonate with CO2, you can set it and forget, high pressure carb it, or do the shaking method.
Set and Forget it: Determine the required pressure for a desired level of carbonation (volume of CO2). This can be calculated using a table like the one here,
http://www.northernbrewer.com/documentation/Kegging.pdf. Set your regulator to this pressure and leave the keg connected for about 2 weeks. This method is reliable and I've heard people say they like their beer's flavor slightly better when using this method (I've not kegged enough of my beer to have developed this opinion yet). It does take patience.
High Pressure Carbonating: Described by the other poster, this involveds setting the psi to about 30 for 2-3 days then adjusting your regulator down to the derired serving temp. It works fine, but may results in overcarbonated beer if left on high pressure for too long (would need to vent the keg to relieve the pressure).
Shake Method or Burst Carbonation: Shake the keg by rocking it back and forth on its side while its hooked up. This method can carbonate your beer in 20-30 minutes. Demonstration here, _http://www.youtube.com/watch?v=KUtvdW7NRso.
I hope this helps. Definitely double check for leaks so you don't drain your CO2 tank.