Take the free trolley if you are arriving during the day time from the Gateway Center a block up from Greyhound . Let the driver know that you need off close to the Transportation Center.
At the Transportation Center there is a info desk in the middle to let you know what bay you need and take bus 80x it an express bus so it has limited hours so plan accordingly
80x Outbound Route Schedule
80x Inbound Route Schedule
The rate is 2.00 for the express service but the express buses are nice and I think the one that goes to Concord is a luxury liner