On iPhone? Get Vision on the App Store.
Installing
Open the disk image and drag Vision into your Applications folder. This step is not cosmetic. Vision blocks apps and websites through a small background component that macOS will only install for an app that lives in Applications, so running it from your Downloads folder leaves sessions running with nothing actually blocked. Vision will warn you if it finds itself in the wrong place.
The first launch
The first time you start a session, macOS asks you to approve Vision in System Settings, under General, then Login Items and Extensions. Blocking cannot work until you do. This is the same approval every focus app on macOS needs, and you only give it once.
Updates
Vision updates itself. It checks for new versions in the background and asks before installing anything, and it will never interrupt a session that is already running: an update waits until you have finished. You can also check whenever you like from the Vision menu.