Doing it this way, I'm not sure it erases the disk and starts from scratch unless you use disk utility, I believe? That was something I wanted to do, erase the disk and start fresh. But I might be wrong if that process DOES erase the diskI don't remember the exact steps but reboot and hold Option Command R until something happens on the screen. Then select reinstall MacOS from the menu that appears. At some point it will ask you to pick a wifi network and enter the password. Then it will download and install a fresh copy. It takes about an hour.