He might have a couple of samples of his own answers on them.

He'll invite the students to add their own tags.

Students can click anywhere on the wall to start their own tag.

Their name at the top (which will come out in red), then just type in the white box below.

When you're all done typing, click anywhere else on the screen. At the very end, click the little origami in the top right corner to get to the home screen and the logout (I hope!).

All the walls like this (except this one) are password-protected, so no one except Pastor Cahill, his confirmation students and their parents can read or write on these walls.