Apple: https://apps.apple.com/us/app/pax-mobile-app/id1594242481
Android: https://play.google.com/store/apps/details?id=com.guidebook.apps.paxwest16.android (Please ignore the url text, its the right one)
If you have the general "Guidebook" app already you can also search PAX and East 2022 will come up.
Leave early. Use services like Track the T and the mobile app YourBus MBTA (Android, dunno about iOS or Win) to get an idea of when things are coming, but those aren't absolute. Us Bostonians will be able to give y'all a better idea of what travel will be like closer to PAX but as of right now I'd recommend leaving at least 1 hour, to 1.5 hours of travel time on the MBTA itself before you want to get there.