Three of the four things that matter are straightforward on Squarespace. The fourth, your robots.txt, you cannot change at all, and knowing that up front saves you an hour looking for a screen that does not exist.
1. Add structured data
Code injection is the cleanest implementation of this on any of the major builders. Settings, Advanced, Code Injection, and the Header box applies to every page immediately. The steps.
2. Switch on your llms.txt
Version 7.1 has a built-in panel for it, switched off by default, so having one is a decision rather than something that happens to you. Squarespace describes it as a proposed standard still in development, which is the same thing we say about it. Where the panel is.
3. Rewrite your opening lines
The slowest and the most valuable. What an engine can and cannot quote. Then give every page its own title, summary and main heading: where they are on Squarespace.
4. Your robots.txt, which you cannot edit
Squarespace serves its own as a system route. Code injection does not reach it and a URL redirect does not override it. Before assuming that is your problem, open yourdomain.com/robots.txt and read it: on most Squarespace sites it is not what is blocking anything. How to tell, and what to do if it is.