You do need to set the cam timing accurately.

I would bin the haynes manual at this point.

Turn the crankshaft anticlockwise back to 90 degrees before TDC (this places the pistons down the bores so contact with the valves is not possible).

Next, set the positions of the camshafts so the timing markings on the sprockets line up and insert the locking tool.

Carefully return the crankshaft to the TDC position and lock in place. Turn it clockwise by 90 degrees to this position.

Fit the timing belt normally, set tension and turn through 2 turns clockwise to the TDC position and check the cam shafts are correctly timed and tension remains correct.