Prerequisites for the tutorial:

Students should be able to run topcat, e.g.:

java -jar topcat-full.jar

(though there are other ways to do it).
They should also be able to run STILTS.  They should be able to execute the command:

java -jar stilts.jar tpipe in=:skysim:3 cmd="keepcols 'ra dec'"

(though "java -jar stilts.jar" might be replaced with "stilts" or something else), giving output something like

Table name: SimulatedSky-3
Description: Simulated star catalogue, based on Gaia EDR3
HealpixLevel: 5
+-----------+------------+
| ra        | dec        |
+-----------+------------+
| 104.37142 | 29.448921  |
| 286.89078 | -53.885025 |
| 184.97084 | -64.85177  |
+-----------+------------+