How do I put one of my forms on a page of my site?

Use “Place a form” in the site editor. It goes on the page as its own section and takes your site’s colors and fonts. You can start from Forms too: open the form and tap “Place it on a page”, which opens the editor with that form picked.

After that, change the form’s questions any time in Forms; the page updates on its own. On a live site, editor changes are a draft until you tap Publish changes on Site. Undo in the editor takes the form back off.