"I finished it yesterday."
Translation:Je l'ai terminé hier.
I believe that the two parts of passe compose (the conjugated avoir/etre and the past participle) are considered one unit. So the direct and indirect pronouns go before avoir/etre.
I think (but am not sure) that when you have two verbs that are not bound together by tense construction (e.g. je veux voir) then the direct and indirect pronouns go in front of the verb they refer to (so je veux le voir because you want to see "it".)
Someone feel free to correct me if I'm wrong.