Usually it is either glue or nail. In commercial or apartment building you would often have concrete floors. You would glue down hardwood in these areas. Given that the building is temperature controlled, the concrete would have very little seasonal movement.
In a residential setting you can glue down hardwood - this is really a call the manufacturer makes. But you must have very flat/clean floors and I have primed before gluing to wood. You have 5" wide boards too. I can't ever recall gluing down wood that wide, especially on wood. The expansion contraction of wood is much greater width wise than with the grain. In short, you just need to nail this stuff down.
As for installation after 3 days, where was it before? If it was in the showroom somewhere then probably. If it was sitting in a cold warehouse then you probably need to give it more time. If you don't know, you need to give it more time. I wait at least 10-14 days before installing.