[Swampdude]

Assuming you mean driven wheels:
There's 2 basic ways of mounting drive wheels:

1. You mount the sprocket to the wheel and leave the bearings in the wheel. Then use bushings to space and center the wheel where you want for chain alignment. This assumes you have a coupling or bolt pattern in the wheel hub that matches your sprocket. Then spacers to hold the sprocket out off the wheel.

2. You take the bearings out of the wheel hub and put a bushing in their place, that hub/bushing is either pinned or keyed to the shaft. Then you either set screw, key or pin your sprocket to that same shaft. Then 3rd you put bearings in the frame to allow the axle to spin.

Chain tension:
Option 1 allows you to slide the wheel back and forth if you make a slot in your frame. So you pull the wheel tight and then tighten the axle.

Option 2 would either require you to slide the drive/motor side to tension the chain or you'll have to add a chain tensioner. This is because your axle bearings are going to be locked in place. Although you'll see a lot of teams use pillow block bearings that can be slid for/aft to tension the chain.

Otherwise if your just mounting a free axle, use a bolt/locknut/washer combo.