This reproduced bezel is made from a material slightly stiffer than the original,
and a certain level of caution is recommended when folding the tabs to secure
the lens:

Start by carefully folding the tabs with a set of pliers.
Place the lens in its proper position in the bezel.
Turn the unit, lens facing upwards, and apply pressure until tabs are completely folded.
A small hammer to tap with might come in handy.