You have to adjust the straps

The second step consists in putting the helmet on and fastening the buckle. Be sure that the front is where it should be, in the front. There is a technique to do this, and it's called the "Eye-Ear-Mouth" test developed by the Bicycle Coalition of Maine:

- When you look upward the front rim should be barely visible to your eye.
- The Y of the side straps should meet just below your ears
- The chin strap should be snug against your chin so that when you open your mouth very wide you can feel the helmet pull down a little bit.

Wearing the helmet now adjust the length of the rear straps, then the length of the front straps, to locate the Y fitting just under your ear. That may involve sliding the straps across the top of the helmet to get the length even on both sides. Now adjust the length of the chin strap so it is comfortably snug. If it cuts into the chin and is not comfortable, then it is too tight. Now pay attention to the rear stabilizer if the helmet has one. It can keep the helmet from jiggling in normal use and make it feel more stable, but only a well-adjusted strap can keep it on in a crash.

When you feel the straps are about right try shaking your head around violently. Then put your palm under the front edge and push up and back. If you can move the helmet more than an inch or so from level, then you need to tighten the strap in front of your ear, and maybe loosen a little more the rear strap behind your ear. Again, the two straps should meet just below your ear. Now reach back and grab the back edge. Pull up. If you can move the helmet more than an inch, tighten the rear strap.

For a final check, you have to move the helmet side to side and front to back, and the skin around the eyebrows should move slightly with the helmet. If it doesn't, then the fit pads are probably too thin in front or back, you need thicker pads.

Once you are done, your helmet should be level, should feel solid on your head and be comfortable. It should pass the eye-ear-mouth test. You shouldn't feel it most of the time, that means it's set correctly. If it still does not fit that way, try again with the straps and pads, or try another helmet.