You have to combine a couple of different methods, but basically line everything up reasonably well, gently lower the bridge (baring in mind it wont be lined up), place the bridge screws in if possible, but tighten them only so far as the bridge will be kept vaguely in place, Then you can combine gently wiggling of the bridge (which i do with a cot covered finger) manipulating of the wheels with pegwood (at which time you'll want to let up on any downward pressure on the bridge), and with great care, patience and perhaps a good eye -- to see which wheel is off two degrees in what direction -- you can usually line it up so that everything will slip into place. tightening the bridge screws gradually as you go, checking for problems, once you think you have it, continue to finish tightening the screws but do keep checking for problems, see if the gear train runs properly, if it doesn't you might make matters worse by screwing the bridge down firmly.
That's the approach that works for me anyway, others might have better things to say.