There is a lot we don't know about monads which makes answering that hard.
Do Monads pick up anything from their host? If they do, then that may be where they gain their knowledge. If they don't, then I guess they would have to "figure out" how to cast, and learn their spells the way everyone else does...
But given how much info is available in the matrix, that might not be too far fetched. After all formula are available online, as are tutors...
Which puts forth some additional questions: wouls a Monad physical adept have a different power point distribution from the host???
Personally, I think it was left an open question so tables can answer it themselves...