The attendants (both trainers and trainees) are supposed to arrange the accommodation by themselves. The following are just a few suggestions where to look, you can of course consult e.g. www.booking.com. The Malá Strana neighborhood, where the school is located, is largely living from tourists, so prices are high and services of shifting quality.
If you have a tight budget, look for a location close to the Metro A Line (the green one, the closer to Malostranská the better) or Trams 20, 12, 15, and 22. Anything that takes you to Újezd or Malostranská is good, too (e.g. Trams 9 and 18). The Metro is quite fast and fool-proof. For instance, it takes just about half an hour to get to Malostranská from Skalka - a distant peripheral neighborhood. The fare in Prague is cheap, especially if you buy a 3-day ticket. There is also a handy mobile app for seeking connections and buying tickets online.
cca 10 min by tram or 20 min by foot to the Training school location
cca 15 min by tram or 20 min by foot to the Training school location
cca 25 min (by metro and tram) to the Training school location. This used to be a very shabby communist-style building mainly used as a student conference center. They have allegedly renovated the rooms. Probably not a fancy accommodation, but decent price, nice neighborhood and good transportation to the lectures.
If you want to go even cheaper, there are also hostels in Prague.