Amtrak is really trying to upstage airlines on complicated boarding procedures:
On the day of your trip, check in with a uniformed Amtrak employee who will verify your ticket, and issue you a boarding pass. You will then be directed to the appropriate boarding area to wait for your train. The earlier you check in, the earlier you’ll be in the boarding process. If you don’t check in, you’ll be among the last to board.
Board with Your Assigned Group
About 30 minutes before departure, a boarding call will be announced and you’ll board with your assigned group.
General boarding for passengers traveling in Coach Class will take place in the Great Hall. There will be signs to direct you to the location of your assigned group. Customers who purchased a $20 Priority Boarding Pass for the Legacy Club will be the first Coach Class group to board.
They also recommend arriving at the station at least 45 minutes before departure, to deal with this nonsense. And “boarding gates” will close 5 minutes before
takeoff train departure.