Question: restore imac to factory setting
I am trying to restore an iMac 2009 to factory settings. i se a lot of comments about open utility and hit continue, but I don’t see where on my Mac it says continue. I don’t have a start up disk. I have a new iMac which the Apple store transferred everything from the old Mac to the new one, but forgot to restore old Mac to factory Which they said they would do. Please help restore old Mac to factory setting.
iMac, macOS High Sierra (10.13)