First of all, are these restore disk you have specifically for your model of PowerBook? This are not any other Mac other than a PowerBook?
If they are for your PowerBook G4, then try first putting the disk in the drive and holding down the option key.
This will bring up a menu. This menu will show you the hard drive and CD drive. You should see an icon with a CD with 'Mac OS X Install' Select it. See if that boot from the disk.
If that fails then try resetting the PMU. http://support.apple.com/kb/HT1431
Which I believe should be taking the battery and power off the machine and holding down the power button for five seconds. Placing the battery back in and power adapter, then rebooting.
Best of luck