1. Firstly,  the neck truss rod key is the same Allen wrench (hex key) you use in the small screw in the back of the bolt and knob assembly to put it back to gather. We recommend you always keep this key with the guitar so you can adjust the truss rod, or work on the bolt and knob assembly. 

2. To assemble, make sure you have all the parts (1. bolt with affixed spring retaining washer, 2. spring, 3. teflon washer, 4. knob, 5. hex screw to affix the knob on the back). Put the bolt through the spring with the narrow diameter section of the spring pressing against the fixed washer on the main bolt. Slide the bolt through the body with the threads facing toward the neck and the spring seated in the spring bushing in the body neck mechanism. Then press the bolt against the spring from the front of the guitar. 

3. Looking at the  back of the Guitar, with the bolt protruding, put the white teflon washer on the bolt, then the knob, then the screw through the knob. The square end of the bolt should insert into the square recess in the knob. The hex screw will go through the knob and screw into the bolt.

4. Use the Allen wrench (hex key) to tighten the small hex screw into the back of the main bolt.