You can put the lockring on anytime you want - you don't have to remove them at all. But the cup needs to contact the bearings, which doesn't happen until there is only about 1 lockring worth of thread sticking out.

If you have the correct cup not cross-threaded on the correct side with grease on the threads, then the cup should turn in relatively easy. Sometimes the threads inside the frame can be rough and require a little force, but if that force is so large that a pin spanner can't possibly turn it, that means something is wrong or the threads need to cleaned up with a thread-chasing tool at a bike shop.

The general idea here is that the cup should allow fairly easy fine bearing adjustment, and that's not going to happen if you need a hammer. You should be able to turn and hold the cup with a relatively simple tool while the lockring is tightened.



Regardless of whether it appears symmetrical to the eye or not, put the spindle in so any lettering it has in the middle could be read by the rider looking down at it - left to right.