Since duolingo claims to be a location where one can "learn" a language, Spanish, for example, where can actual instructions on the the various topics be found?
Exactly. What I like about Duo is that I have to figure the language out. If they started giving instructions it'd be a snoozefest and I'd probably stop using it. Anyway, as far as finding actual instructions, you have to use Duo in conjunction with other resources. Posting your specific grammar/vocabulary/what-have-you question in the forums for other users to answer is another option.