Install High Sierra on MacBook Pro 2012
My MacBook Pro (13-inch, Mid 2012) has Catalina and Mojave installed on separate AFPS volumes. I want to install High Sierra as well. I have created a High Sierra volume and downloaded High Sierra from the App Store. I then created a bootable High Sierra USB. Can anybody explain how I proceed and install to the High Sierra volume please.
[Re-Titled by Moderator]