SteamVR selecting menu items with head movement?

Im using SteamVR in a quest pro (the steamvr menu system look fantastic now) and have noticed in the middle of the screen is a round selecting tool that highlights things when I look at them https://mobdro.bio/ .

Its not eye tracked, its just centre of your view.

I just cant for the life of me work out how to SELECT (click?)

I look/aim at a game in my library, it highlights but then I have no way to SELECT and so I have to fumble around for my controller to point and click.

Has anyone worked out how to click? I tried blinking, pressing the volume up/down, pinching fingers.

Many thanks as it would be much cooler to just use this gaze selector thats clearly built for this purpose right?