Bootstrap, at the green boot up menu install from sd card, navigate to the folder your zip is in (the parent directory, not a folder you've unzipped) select full blur or stock, its up to you, enter once its installed make sure you have data mounted (it will say unmount if it is) this is under the first option in the green boot up menu. Power gets you back a step in this menu, select reboot now and give it a good 5 min to boot up and you're good. I assume you're coming from stock rooted rom, therefore no need to dump data or cache