No advance notification or formal written referral is necessary to attend an Al-Anon meeting. There is no registration. The meetings are on a walk-in basis (when in-person). Al‑Anon has no membership list and does not take attendance. You’re welcome to attend as frequently or infrequently as you choose. There is never any obligation.
For temporary virtual meetings, just connect at the appropriate day and time. For face-to-face meetings when they are in session, just arrive a few minutes before the meeting starts.