First thing....wear glasses or goggles.
Get the headlight oriented correctly in the bezel and put the short end of one clip under the sharp back edge of the bezel, with the "elbow" pointing out so that the bend rests on the rear rim of the glass.
Keep pressure on the whole clip whilst also forcing the long end under the back edge of the bezel.
You sort of need three hands as the next clip is best fitted at approximately 120 degrees from the first.
By then, it should be fairly secure and you can put in a third. Sometimes I have used four clips.
Those new style clips are fairly stiff, but work well.