Thankfully I am technically minded, and worked out the case is in two parts within a couple of seconds. Although, the none technically minded will find it difficult.
1. Hold the plastic/rubber case in your right/left hand. Looking at the power/volume buttons on the right side of the case.
2. Squeeze the sides of the case with your right/left thumb and the rubber sleeve will come apart from the plastic case.
3. Pull the rubber sleeve out of the plastic exoskeleton backing and pull this apart.
4. Slide your HTC One Max into the rubber sleeve, the rubber sleeve is a little hard on the corners. I found it easier to go from top to bottom.
5. Snap on the exoskeleton backing of the case onto the back of the rubber sleeve, again bearing in mind the corners are a little on the hard side. but with a strong push it will clip on.
This case is a fantastic product and would protect your phone in the event of you dropping it to the floor. The only gripe that I have is the two ridges on the exoskeleton backing near where the biometric scanner is located on the rear of the phone. These are in the way and you cannot successfully scan your designated finger. Unless you have tiny fingers then you'll be fine. Which in my case is... Hands like shovels. other than that this is a great solid case and would most definitely protect your phone in the unlikely event of you accidently dropping your phone. and deserves 5 stars for protection, but it is left down with access to the biometric scanner on the rear access of the case.