Your boot guy that sold you the boots should be able to help you with this. If not, then you can adjust the cuff effectively yourself if you pay attention to details and take your time. Like the others said, finding a pro boot fitter is the best way to go.
A full length mirror is needed for the best DIY job IMO. Follow these steps and you should get the job done fairly well.
No clothing over your calf or foot, but ski socks are OK. I prefer to have only skin showing on my calf so I wear shorts with nothing on my legs or feet.
Remove the liner from your boot, but you should place whatever footbed or insole you will normally be wearing inside the boot to stand on while you make this adjustment.
Make sure you are in front of the mirror and gently get in your boots (soft skin against hard plastic can scrape and hurt). find your normal skiing width between your feet and then make sure that your boots are parallel to each other. If your have trouble with getting or keeping them parallel then place some tape on the floor as a guide to reference the parallel position to and the fore aft position of the boots to each other as well.
With boots parallel, get your foot in a centered position by gently sliding your heel side to side and then stopping your foot in the middle. Make sure that your foot is comfortably in the footbed like it should be.
Now match the forward lean with your lower leg angle and look in the mirror to see if your leg has equal room between each side of the cuff and your leg. Now make a small adjustment to one side or the other and recheck for equal space on each side of the leg. It is important to keep your ski boots in the same position when going through the adjustment process. This is where the tape is also be a good idea. It allows you to step out of your position, make the needed adjustment, and then step back into position to check the adjustment. Take your time and be methodical about the process and get your foot centered each time you make an assessment. Remember as well that you may have adjustments on both the inside of the cuff and the outside of the cuff. I believe the M-100 has both sides adjustable.
Good luck and let us know how it goes.