Start with these relationships:
Actors::__pkActorID = Characters::_fkActorID
Movies::__pkMovieID = Characters::_fkMovieID
You can place a portal to Characters on the Actors layout to list and select Movies records for each given Actors record. Fields from Movies can be included in the Portal to show additional info about each selected Movies record and the _fkMovieID field can be set up with a value list for selecting Movies records by their ID field.
For an explanation of the notation that I am using, see the first post of: Common Forum Relationship and Field Notations Explained