place the spring plate cover back in place and bolt on losely.
place jack under the spring plate and lift up until it is clear of the stop lip. now use a rubber mallet to knock the pring plate fully home on its splinesand make sure the spring plate sits back on the stop lip. now do the bolts up on the spring plate cover - this will stop the spring plate slipping off the stop lip
now use the jack to hold the a arm (or axle if swing axle) in the right position and bolt up in place.
Do all bolts upto correct torque setting 72 ft / lbs for spring plate i think but please check your manual! and dont forget to bolt up your shock absorber!
wheels back on and you may want to push forward/ back to let suspension settle although it probably wont fully settle until you have driven it.