The answer to your question is that the black pin protector on the motherboard is to be removed (obviously), and the little "door" that is latched down on the side, holding down the CPU, goes beneath the Tuniq Tower 120.
As a suggestion, I find the easiest way to install the Tuniq Tower is as follows:
1) Place the backplate onto the back of the motherboard in the proper position, then lay the motherboard flat on the ground (with the usable side facing up) on an anti-static surface, such as the plastic packaging the motherboard came in. If you do not have the tape on the backplate anymore for whatever reason, cutting double-sided tape into rectangles and placing it on the part of the backplate that contacts the motherboard (it looks like a square "ridge", sticking up from the rest of the backplate) works well.
2) Put the CPU in the socket, properly oriented, and lock it down.
3) Apply the thermal paste in whatever fashion suits you; do not use too much. I prefer to put a grain of rice in the center, then stretch a plastic bag over my finger and use that to spread the paste evenly about the CPU IHS (the plastic bag is to prevent finger prints from propagating into the thermal paste pattern, and to keep your finger clean!).
4) Place the Tuniq Tower 120 (without the fan holder) onto the socket, with the H-bracket in place and centered on the little knob that is for that purpose. (Be sure to orient the tower such that when the fan holder is placed into the Tuniq Tower 120, the air blows toward the back of the case!)
5) Screw in a corner halfway, then screw in the opposite corner all the way, then finish up the original corner. Do the same with the remaining two corners, and when those are done, tighten all 4 screws as far as possible. You should be able to get all of the screws down such that you cannot see thread on any of them anymore when looking at the usable side of the motherboard.
6) With the Tuniq Tower 120 now securely attached, drop the fan holder into its slot and screw it in.
7) Install the motherboard and you're off!