. This title appears to be a misidentification or an extremely niche fan-reference, possibly related to the popular series Oshi no Ko , which does have an extensive dub.
So the literal meaning:
Go to Media > Open Multiple Files , add your video, check "Show more options", select "Play another media synchronously", and add the audio file. Quick, one-time viewing without file editing. shinseki no ko to o tomari dakara dub install
A corrected natural Japanese phrase could be: ("Because I'm having a sleepover with my cousin, I'll install the dub [version of the game/anime]") add your video