In order to board Brio you must pay BEFORE you board. All Brio stations have ticket vending machines where you will need to buy your ticket first. You can purchase a single-trip ticket, a day pass, a weekly pass or a monthly pass at a ticket vending machine.
Once you have your pass you simply board the Brio vehicle through any door. Remember, you MUST be prepared to show proof of payment (and a valid ID if using a reduced fare ticket/pass) if asked by any Sun Metro employee. Failure to pay may result in being banned from riding Brio and being fined for fare evasion.