You use the accusative form (Atroksie) for the object of the sentence, meaning for the noun that's on the recieving end of the verb. So I see the owl, the owl is the one being seen. The nominative form (Atroksia) is used for the subject of the sentence, meaning the one doing the verb. In the above example, I'm the one doing the seeing, so I'm the subject of the verb. With some verbs, like Edrus (sleeping), the one doing the action is also recieving it (you don't "sleep someone" else), and in that case the one doing the verb is both the subject and the object of the sentence, but appears in the nominative form (So it's vala edrus, rather than vale edrus)
Pronunciation help: There were a lot Rs and I know the basic lesson says that all Rs are trilled but is that a hard rule? For instance, is it there at the begining of Rini? Is it there in urnes/urnen? Atroski? Would the last three be clipped Rs like the last R in dolor (Spanish: pain)?