I got one of these trainers second hand without the manual and I am unable to fit my bike onto it nor adjust the resistance toggle and it’s incredibly frustrating so I hope someone might be able to help out.
See if this this link is helpful.
You will need their special skewer to fix the rear wheel in the trainer, did you get that with the purchase? If your bike has disc brakes it can be a problem.
The manual you linked is for the head unit.
This is the Fortius installation manual, but apart from the brake unit, the rest of the hardware is identical. Maybe this can help.
Resistance is set by the head unit so it’s not totally irrelevant.
Agreed. It’s relevant to the second part of the question (I think - that part is not very clear).