I have the previous one (Mk6) which has 8 different modes. All you do is when it’s off hold down the on button for quite a while and on mine the 8 LEDs on the back light up, first one, then two, then three, etc. The number of lit LEDs equals the mode you’re putting it in. Once you have the right number of LEDs lit up then you take up finger off the button and it saves that mode.
Then when using the light you get the high, medium and low settings which correspond to the mode it’s in.
The Mk7 has 10 modes and a different display and button but I presume it works the same – hold the button down and let it count up to the mode you want, then release the button. It’s quite hard to explain but very simple in practice.