Hi Andrew,
If you create a space and go to either the Projects or the Members page, you should see a button at the bottom of the Options panel on the right for requesting additional capacity, like so:

If you're not seeing that button, is it possible that you have a paid account on shinyapps.io? If so, we grant you additional capacity on Cloud, so you'd be all set to run your training course without having to request additional capacity.
Hope this helps!
Robby