Present puts your structure on the whole screen and turns it slowly, with nothing else on it. It is for the ten minutes before a meeting starts, while people are arriving and taking their seats, or for a stand at an exhibition where the screen has to do the work of stopping somebody walking past.
Presenting from the app is a Pro feature, along with the other ways of putting a document in front of somebody. See Account & Billing. It still travels with anything you have already published: a share link or a downloaded file carries its own Present button, whoever opens it.
They sit along the bottom, and they fade away with the cursor after a few seconds of stillness, so a screen nobody is touching shows your work and nothing else. Move the mouse and they come back.
The canvas is deliberately inert while you are presenting, so a stray hand on the mouse or a knock of the table cannot spin your structure or open a page in front of everybody. The keyboard is ignored too, apart from Escape.
This is not only for your own screen. Every link you publish and every HTML file you export carries the same button in the row of controls under its graph, so whoever you sent it to can put it up in their own meeting, without you there and without installing anything.
To build the document in the first place, see Publisher Studio: Basics. To get it to somebody, see Publisher Studio: Sharing.
Still stuck? Email support@filamental.space.