Set the mudguard brackets to give about 20-25mm clearance, depending on whether you want to be doing any muddy green-laneing.
This may involve adjusting the position of the M6 holes on the brackets.
Bolt the brackets on and fit the wheels.
The fibreglass guards can be bonded to the brackets with the Triking issued PU adhesive (black stuff). Abraid the gluing area with coarse paper to give a good adhesive key. Put a generous helping of black stuff on the bracket.
To hold them in the correct position, I bent up a set of flat bars which could be gripped together with rubber bands. Simple. You have plenty of time to fiddle around with them to get the perfect position. You will have plenty of room to get a gloved finger under the guard to feather out the oozed out glue.
You may want to take 2 days over this to allow the adhesive to set before taking the elastic bands off and starting the other side.
A good position for the leading edge of the guard is for it to cover the wheel rim (not the tyre) when viewed vertically. This an MSVA requirement, read the manual!
You may need a prop or wedge here and there.