Erase Macbook pro

You can follow the directions here, same as what to do when you sell your Mac.

What to do before selling or giving away your Mac - Apple Support

Be sure you have a good backup either Time Machine or, a cloning software like SuperDuper! or CarbonCopy Cloner.

The advanage of the clone is that it is bootable. The advantage of TM is that it creates recursive backup, so you can restore a file or the entire drive from a certain point in time.

Startup holding option + command + R keys, or from your install disks if they shipped with your system. Then in Disk Utility choose your entire hard drive upper most icon and erase. It will install the system that shipped with your Mac. Upgrade to El Capitan and then follow Setup Assistant.

Reformatting the drive from Recovery using the Disk utility—this will erase and start over.

Recovery http://support.apple.com/kb/HT4718

More on backing up How to create a boot clone

You may not have access to El Capitan once you erase. Recovery will more than likely present you with the OS X that shipped with your Mac. Then from there you can have to upgrade to 10.11 or before hand:

http://osxdaily.com/2015/09/30/create-os-x-el-capitan-boot-install-drive/

Nice User Tip! I'd click on some button there, but I'm afraid if I do I'll get some kind of merit badge slapped on my icon. I'm trying to keep it clean!😎

macjack wrote:

Nice User Tip! I'd click on some button there, but I'm afraid if I do I'll get some kind of merit badge slapped on my icon. I'm trying to keep it clean!😎

Thanks. No merit badge for simply "liking" a Tip.... That's all I can say however 😉

Done!

Legion5 wrote:

Awesome, My HDD is new and has El Capitan on it, will it keep the OS since it is the only one on the HDD?

• If you use the Recovery System stored on your startup drive to reinstall OS X, it installs the most recent version of OS X previously installed on this computer.
• If you use Internet Recovery to reinstall OS X, it installs the version of OS X that originally came with your computer. After installation is finished, use the Mac App Store to install related updates or later versions of OS X that you have previously purchased.

Recovery http://support.apple.com/kb/HT4718

No, the it will be erased, it will install the system that shipped with your Mac.