If the ends of your axle look similar to this top pic, I agree with surfs up post.
These racekart style axles are designed to use racekart style wheel hubs, that have built-in locking collars like this pic below: When those 2 Allen head clamp bolts are tightened, the hub grips the axle
very-very securely.
Some of these wheel hub only have 1-clamp bolt, they work fine too.
The snap ring installed around the end of the axle is simply used for extra insurance that the hub could never slide off the axle, in case the clamp bolts were to loosen up while riding...
You wouldnt need to use any additional locking-clamps or spacers to help hold the hub in place to the axle:
Then after the hub/wheel/tire is all installed, your final step is to simply instal the snap ring on the very ends of your axle. The wheel hub can be slid/located on the axle to whatever track-width makes your kart handle its best. You dont necessarily need to adjust the wheel hubs out as far outward as possible, but you could if you want: