How the two connect: the patient invites you
From their Sharing page, a patient sends an invitation to your email, choosing your access level and relationship as they do. You open the link, sign in — or create a caregiver account, with the type pre-selected for you — and their record appears in your patient switcher. Invitations expire after a while, so open them promptly; the patient can always send a fresh one.
From the patient's side, this is Share access & invite caregivers.