The recovery discs will erase all data on the drive, so make sure you have backups of important data FIRST. After that, you put the disc in the drive, and then when you see the Toshiba logo there should be a message about pressing some key for a boot menu. I want to think it is F12, or maybe Del, but you should verify that with what you see on screen.
This will bring you to a menu where you can choose which device to boot from, and you want to select the DVD/CD drive. Then just wait for things to load and follow the instructions on the screen.