For a three-act plot analysis, put on your screenwriter’s hat. Moviemakers know the formula well: at the end of Act One, the main character is drawn in completely to a conflict. During Act Two, she is farthest away from her goals. At the end of Act Three, the story is resolved.
Act I
Aeneas arrives in Libya and starts a love affair with Dido, thereby jeopardizing his future.
Act II
Aeneas leaves Dido and goes to the underworld where Anchises shows him a lot of cool stuff about the future.
Act III
Aeneas goes to Italy and kills a bunch of guys, including Turnus, thereby securing said future.