You will need the disks that came with your Mac Book Pro. If you do not have them you can order them from Apple or even find them online. You would boot to the Mac Book Pro DVD and follow the prompts to blow away your install and install a fresh clean OS X partition. Make sure you back up your data first as the machine will be just like it was from the factory.
You can also take it to an apple store and have it done for you.
First of all backup your data and insert installation DVD and boot it, it will prompt you for language choose after that there will be setup guide follow and have a clean copy , u can use utility to format or repartition your hard drive .