The old bezel should have the snap into place pins. use plastic weld to glue new plastic pins onto the new bezel using the old original one as a guide to glue them into the proper position(be sure the pins are the same diameter as the ones on the original)...then let the the glue dry and cure for a day. The bezel should snap into place like the original
If they are the type that require screws...the same method applies, just be sure that they are plastic!!