The ZIMANOX replaces the left crank arm on most Shimano crank sets.
Remove the cap covering the hole in the spindle. Use a 5 mm hex key to remove the two bolts. Lift the little safety clip with a small screwdriver. Pull the Shimano crank arm off.
Mount your new ZIMANOX in its place. Reuse bolts, washers and the safety clip. Remember to grease the bolt threads before mounting.
Tighten the two bolts to 12-14 Nm (very firm). Alternate between tightening one and the other a few times. You can also mount the spindle cap again.
See also the full user manual for more details.
Simple video showing the installation.