This should install the version of OS X that was pre-installed when the computer was new. Erase Mac Hard Drive by Using Disk Utility. Select Reinstall OS X and click on the Continue button.Quit Disk Utility and return to the Utility Menu.Click on the Apply button, then click on the Done button when it activates.
To do that, the only thing you need is a bit of precise syntax to make sure that you are erasing the proper disk. But some Mac users might need to erase them from the command line on Mac OS. Below are the steps to reinstall a clean copy of OS X after erasing the disk. Most users use Disk Utility to erase a disk or hard drive. Just press and hold the power button on your Mac until it turns off.I don't know exactly which model you have, but you can do a Network Restore provided your model is from Late-2011 or later.
If you're selling, giving away, or trading-in your Mac and want to leave it in an out-of-box state, don't use the setup assistant or your previously connected Bluetooth devices, if any.
Or click Continue to proceed without making a new backup.