You'll need to loosen all 4.

I used a pipe wrench when I couldn't just roll the quad to move the axle.

Since I'm not a plumber, and don't need a high dollar tool, I just picked up a big one at harbor freight.

Don't forget to print the 20% off coupon too.

 

Here's how you do it as instructed by my old Polaris Manual
from 1999. The only thing that it doesn't show clearly in the manual is the caliper bolt that you loosen which is on the bottom of the rear brake caliper. To find the slot that the punch pin goes into on the rear sprocket you have to roll the machine forward or backwards until the slot on the rear sprocket lines up with the hole in the hub.

It will also help to have a decent wrench set when adjusting the chain. You can put a wrench on the bottom locking nut and the socket on the top of the bolt to loosen or tighten them. If you use a power tool to loosen the locking nut be careful because you can damage the teflon threads in them with too much heat and pressure and then have to replace them.