The Point of Sale feature functions as a cash register for simple sales transactions.
Sales may be processed as anonymous purchases (to a generic buyer) or to a specific buyer (by selecting an existing user record or entering the customers info to create a new record.
The POS feature is intended for auxiliary use (eg selling raffle tickets at a PTA meeting, selling concessions or merchandise) where customers are making purchases in person. During your gala, cash payments for incidentals and charging purchases to a bidder number are recommended (POS transactions generate different receipts and reporting).
Go to Admin > Site Settings > POS > General
(If POS does not display on your Site Settings Menu, contact support.)