It should be a bolt in, unless your car was modified to install the rear that's in it now. If you've got factory upper and lower control arms then there's not really any adjustment possible - you'll just get what you get. However it's still good to double check it to see where you're at. Any front end alignment shop that can do "4-wheel" alignments should be able to tell you if the axle is square in the car (actually square with the front axle). There are lots of reference sites on the internet that describe how to check your drive shaft angle. Here's one: DRIVE LINE PHASING
Generally, the procedure is to get the car high up in the air and support the frame with jack stands, support the rear axle at normal ride height with a good floor jack.
Disconnect the shocks from the rear axle.
Disconnect the drive shaft
Disconnect (and plug) the brake lines at the T fitting on the axle.
Disconnect the parking brake cables at the connectors just in front of the lower control arm frame mounts.
Use the floor jack to position the axle up or down so that the control arm bushings aren't in a bind.
Remove ONE of the upper control arm bolts on just one side (which end doesn't matter - do the easiest to get to)
Thread a piece of rope, chain, wire, etc through the center of each rear spring top to bottom (or bottom to top) and around the axle tube. Leave the loop "loose" enough so that when the spring expands fully it won't be in a bind, but only just. This is a safety precaution.
Tie a rope or something from the unbolted upper control arm mount on the axle to the frame. The intent here is to have something in place to keep the axle from flopping over backwards when you lower it later.
Remove one of the other upper control arm bolts on the other side.
At this point, the only things keeping the axle from flopping over forwards or backwards are the lower control arms and the springs and what you tied to the upper control arm mount, so be careful.
Slowly lower the floor jack to relase the tension on the springs. When they get loose enough they may pop out. That's why you tied them through the center - so that they can't throw themselves at your head when they come loose. If they don't come out on their own, pull them out by hand but again - be careful.
Push the axle forward so that it sort of "lays over" onto the lower control arms.
Unbolt the lower control arms (usually at the frame end) and use the jack to lower and remove the axle. You'll probably want some help to keep it balanced on the jack while someone else is operating the jack.
Installation is pretty much the reverse sequence. Don't forget to reconnect and bleed the brakes. Sometimes it takes some finagling with the jack, moving the axle up or down, to be able to get all the control arm bolts in. There is a correct orientation for the springs - how they're "clocked" and seated into the upper spring perches - so pay attention to how they're oriented before you relase the tension on them so you can reinstall them in the same positions.