not a teacher
Participants interested in signing up for a workshop should mark their names at the reception desk in the lobby.
It isn't clear whether there is already a list of names at the desk, or a list has to be made up.
If there is already a list of names you might be asked to "mark", "check", "tick" etc, your name to show your interest.
If there is not yet a list, you are likely to be asked to "leave your name" at the desk.
The person at the desk takes your name.