This article is about the Proxi admin app at app.proxi.co.
Squarespace takes the Proxi embed code in a Code block or an Embed block.
Steps
In Proxi, copy the embed code (see Adding Proxi to Your Website: Which Code to Use).
Edit the page, click an insert point, and add a Code block. Leave the type set to HTML (not Markdown).
Paste the code and save.
Good to Know
The Code block needs a Core plan or above. On the Personal plan, use an Embed block instead: add it, click the </> icon to switch to code mode, and paste the same embed code.
It may look hidden while you're logged in. Squarespace sometimes doesn't render custom code for the person editing the site. Open the page in a private window to see what visitors see.
Custom code can misbehave inside an Index page section on some templates. If it doesn't appear, try a regular page.