Open Room Settings → Members to see who belongs to the room. Available actions depend on your role.
Give someone more access
A member can make a guest a member. Only the owner can make someone an admin or remove their admin role.
Remove, kick, or ban
Kicking makes someone leave now. A member may return unless the door is closed; a guest needs to knock again. A ban stops someone returning until it is removed. The owner and admins can manage members and guests; only the owner can act on admins.
Undo a ban
Go to Room Settings → Members → Banned, open the person's menu, and choose Unban.
Turn off a camera or mic
The owner or an admin can do this from the person's camera menu or the members list. It is a one-time action, and the person can turn their device back on.