Choose a new password. You'll stay signed in here, but any other device you're signed in on will be signed out.

Adding someone authorises their email and invites them. They click the link, choose their own password, and they're in — clicking the link is what proves the address is theirs, so there's no separate verification step. Send invite emails it for you; Copy link gives you the same link to paste into your own email, which is useful while email sending is still being set up. Removing someone revokes access immediately, including any live session.