I have a software to wipe off the hard drive of my computer but I don't know how to boot it so that I can use the software. I do not want to reinstall anything because I am going to sell it. thank you

You need to go into your system setup and change your boot frive to the CD.

I believe that you need to press F2 as you power on the PC to get to system setup.

This depends on the software. Generally such software can be run from a disk either after booting to booting to the disk. What does the software's instructions say?

Just to add to the simplicity, some CDs will use AUTORUN.inf to automatically start the CD as soon as it's loaded.