How do I use these plays in my class or small group?
Just have the group sit around a table or in a circle as they normally would, pass out copies of the play, assign parts, and start reading! You might also want to read the Gospel passage itself beforehand, though this isn't required to follow the action in the plays.
Can these plays be performed in front of an audience?
They weren't really written to be performed on stage, or even to be read aloud to an audience, so you'd probably have to make some adjustments for them to work well either way. But you certainly have my permission to try!
What if my church doesn't go by the lectionary?
You can use the plays in any order you like, and I've provided additional sorting options above to help you browse through them in various ways.