The collective rocker assembly is fitted to the mainframes as shown below.
The screw highlighted in red on the right hand picture should not be overtightened.
Overtightening this screw or it's counterpart on the opposite side will cause the elevator to be very stiff or notchy.

Next task is to fit the main gear and the main mast with the rotor head attached.
The main gear is just pushed into the frames loose, the mast goes through the main gear.
Lastley the main gear is secured by a screw with nut through it and the main mast.