Short answer
HubSpot's KB: the dashboard evaluates pages against Web Vitals metrics. It only analyzes HubSpot-hosted content. Open it at app.hubspot.com/site-speed/ followed by your account ID.
1. In HubSpot
The relevant screen in my demo portal.

2. Worth knowing
External sites, such as WordPress, need other tools.
3. Related
Speeding up pages and image resizing.