How does my door come apart on my Over the range Microwave to replace the door handle?....

There is a inner door trim on the inside of the microwave door that can come off to expose the screws for the handle. This trim is held in place by clips built into the trim, ( some older models may also have screws - look for them and remove before going any further ) the tabs on this trim can break easily but with a putty knife and some patience, the trim can be removed to get at the handle screws. See picture help. This trim can be pushed so the clips will "pop" back into place after the handle repair.