The grease filter in a GE Spacemaker microwave traps grease that foods release when cooked on the stove beneath the microwave. The filter also helps keep flames from affecting the bottom of the microwave. GE recommends that you clean the filter at least once a month. If the filter has been in place for a long time, change it instead of simply cleaning it.
Grab the tab on the existing filter and slide the filter to the right.
Pull down, then out.
Slide the new filter into the frame slot under the microwave.
Pull the filter up and to the right to lock it into place.