How do I know when to use the "-n" for an object?
I know that it is supposed to be used for an object, but it doesn't seem to always be used in the course. I think that I'm just not understanding it fully. If someone could explain it to me in a better way, I might understand it. Dankon pro via helpo.
Can you give an example of when you thought there should be a '-n' and the course disagreed with you?
You don't need the ending after a preposition (except, see below), or with 'estas' or 'fariĝas', or any other verb that just describes the subject.
(you do use the '-n' ending after a preposition to show 'movement towards' - 'sur la tablo' "on the table" 'sur la tablon' "onto the table")
Here's the long description: https://lernu.net/en/gramatiko/akuzativo
Here is a good explanation of what accusative case is, how it works and how to apply it in Esperanto.