As mentioned, the easy way would be to get a ground glass back, if it didn’t come with one.
Without it, you might be able to come sort of close by removing the lens and moving the lens standard out to 88mm from the film plane, with the focus track set to the infinity mark on the scale. From that point fine tuning would be exposing a few rolls of film and looking at what’s in focus on the negatives.
Getting a ground glass back is probably a cheaper and faster solution.
It’s probably reasonable to assume that the rangefinder is adjusted to that lens, and has the right lever, but again, you need the ground glass back to verify that.