Turning it on
Open Settings with ⌘, and go to the Edge pane. It is listed on both channels, because it is the only place to turn Edge on. The first row is Enable Edge features, captioned “Early access to features that are still being tested. They may be unstable.” Under it sits a “Features” card with one switch per preview feature, so you can try them one at a time. The card is disabled until the channel switch is on. Turning the channel back off never touches the per-feature switches: a feature you had on stays saved, and comes back exactly as you left it when you turn Edge on again. A feature is available only when both its own switch and the channel switch are on. Turning either one off hides every surface the feature owns.
Settings → Edge: the channel switch and one switch per preview feature, Cost ceiling marked Pro