1. Turn it on under Account settings
Open Account settings (the Profile page), find Weekly digest, tick Send me the weekly digest and save. It is off for every account until someone with notification permissions turns it on. The mail goes to the account's contact address.
2. Know what it covers
The previous Monday-to-Sunday week, in UTC: pooled uptime across every monitor with a list of the lowest-uptime ones, incidents opened, resolved and still open, and for Errors the new issues, regressions, top issues by event count, and the accepted and dropped event totals. Drop counters are kept per calendar month, so the digest reports them month to date and says so. A monitor with no checks counts as no data, never as up, and heartbeat monitors are excluded from the uptime figure and listed as excluded.
3. Preview it now
Send me this week's digest now mails the real digest for the week so far to the same address, marked as a preview. It works before you turn weekly delivery on and never replaces Monday's scheduled send.
4. Stop it with one click
Every digest carries an unsubscribe link in the footer and an RFC 8058 List-Unsubscribe header, so the unsubscribe button in Gmail or Outlook works too. Either turns the digest off for the account; alerts are unaffected. A quiet week is still sent and says, in one line, that nothing happened.
Go deeper
The full reference lives in the docs: Alerting documentation. Error codes named above are each explained in the error-code reference.