How to enable the AI button in the toolbar?

I’ve actually just discovered by accident that it is enabled and working but you need to highlight the text you want to proofread and then click the AI button, which is all very difficult on mobile (I kept clicking Cut by mistake) and not at all discoverable.

So my next question is how to get the toolbar button like they have on Meta?

An image of a computer screen displaying a pop-up window with a 'Cut' command highlighted, and the text 'This could be used for discussions. Try it out before we can use this for forums. We see this for  (Captioned by AI)