Give us some information about your truck. Or put it in a signature so we don't have to ask.
Depending on the truck, you probably need to remove the radio bezel, the plastic under the steering column, and the plastic in front of your gauges. Should be mostly 9/32" or 7mm sockets. Then you can pull out your cluster and change out the burned out bulbs.
Check this out, it might help.
How-To: Replacing Instrument Cluster Lights
Oh, and welcome to RF :)