Many Quantum chairs will have almost identical instructions - but keep in mind each wheelchair user's needs are unique and they use their chairs differently.
Ideally, it is easiest to mount when a wheelchair is not occupied.
Optional:

For this wheelchair we will "sandwich mount" to the tie-down.
Determine the mounting side for best access. (consider avoiding the wheelchair controls)
Before we begin mounting, try to see if there is anything obstructing the mount and post.
It is easiest mounting to a seat with level tilt, so things do not slide around when you detach them.
In this example:
We mount to the right side of the chair,
And this mounting does not require other components to dodge the arm-rest.
The footrest is removed and the arm-rest is folded up in the following pictures for clarity.
Locate the tie-down at the mounting location. There should be two bolts attaching the tie-down.
Using the 1/2" Hex Wrench, remove the bolt by turning it counter-clockwise.
Once completely unscrewed - remove the bolt and set it safely aside.
Do not lose this bolt! You will need it for re-assembly later.
Caution
This bolt has a "slide-nut" on the opposite side. Make sure that this component does not slide out of place.
If it does, you might need a magnet or tool to retrieve it.
Using the 1/2" Hex Wrench, remove the second bolt attached to the tie-down.
Once completely removed, set the tie-down and that short bolt aside.
Once the tie-down is removed, the wheelchair should look like this.
Remove the Wheelchair Adapter Plate 2 (WC-AP2) from its bag.
There are multiple positions and orientations the WC-AP2 can be attached (the WB attaches to two of the threaded holes in this plate)
Position the threaded holes for best attachment of the Wheelchair Bracket.
In this example, the WC-AP2 is positioned so that the wheelchair bracket is as far forward as possible.
Locate the two largest holes on the WC-AP2 and align them with the holes from bolt #1 and #2.
In the bag of screws that comes with the WC-AP2, remove the brass colored bolt.
Use this bolt in place of the short bolt we removed in step #2.
Re-insert these two bolts (the long bolt, and the new, brass bolt) into the tie-down.
Sandwich the WC-AP2 in between the Tie-Down and wheelchair seat frame.
Hand-screw both the bolts (turn clock-wise) back into the fasteners wheelchair seat frame.
Screw both bolts down, using the 1/2" Hex Wrench turning clock-wise to tighten.
Orient the Wheelchair Bracket in the position for best access.
Using a 3/16" Hex Key and the two screws packed with the Wheelchair Bracket, attach it to the WC-AP2.
(Adjustable Wheelchair Bracket (WB) is shown in this example)