Your microwave oven is shipped with the blower assembled for room venting. You need to adjust the blower if you want wall-venting or roof-venting installation.
Electric shock hazard! Unplug unit before working on it.
Do not pull or stretch the blower wiring. Pulling and stretching the blower wiring could result in electric shock.
To avoid risk of property damage, unplug the microwave oven or disconnect the power at the source by removing the fuse or throwing the circuit breaker.
To avoid risk of personal injury, wear protective gloves when handling the mounting plate.
Remove any shipping materials and parts from inside the microwave oven. Set them aside for later use.
Cover the countertop or cooktop with a thick, protective covering to protect it from damage and dirt.

Blanket, cardboard or other covering
If you have a free-standing range, disconnect it, move it onto a piece of cardboard or hardboard and pull it away from the wall, so that you can get closer to the upper cabinet and back wall for easier measuring and drilling.
Locate the exhaust adapter, grease filters and hardware packet.
At this point, remove any adhesive tape (if there is any), on the exhaust adapter, the grease filters and the power supply cord.
This oven is shipped assembled for room-venting.
Remove one or several blower plate mounting screw(s) a and one or two blower unit mounting screw(s) f. Remove the blower plate d from the cabinet.

b Blower unit
c Knockouts
e Back plate
Carefully lift the blower unit out of the microwave oven.

Use side cutters or tin snips to cut out and remove the knockouts b from the back plate a. Be careful not to distort the back plate. Discard the knockouts.

To avoid pinching the blower wire, make sure that it is channeled underneath and between the two exhaust ports when they are rotated.

Rotate and reinstall the blower unit a so that the exhaust ports b face the rear of the cabinet and are aligned with the rear knockouts. When you insert the blower unit, the blower wire c must be routed as shown.

Attach the blower plate d to the microwave oven so the blower unit exhaust ports c and blower plate opening are aligned. Attach one or two blower unit mounting screw(s) f and then one or several blower plate mounting screw(s) a.

b Blower unit
e Back plate
Insert the tabs on each side of the damper into the holes at the inside rear of the adapter. Attach the exhaust adapter a to the back plate wall side. Push in securely until it is past the top locking tabs c and in the lower locking tabs c. Make sure that the damper hinge is at the top and that the damper swings freely.

b Damper (hinge side up)
d Guides on back plate
e Slide exhaust adapter into guides on back plate.
Follow steps 1 and 2 under Wall-Venting Installation.
Rotate and reinstall the blower unit a so that the exhaust ports b face the top of the cabinet. When you insert the blower unit, the blower wire c must be routed as shown.

Attach blower plate d to microwave oven. Attach the one or two blower unit mounting screw(s) f and then the one or several blower plate mounting screw(s) a.

b Blower unit
c Knockouts
e Back plate
Insert the tabs on each side of the damper into the holes at the inside rear of the adapter. Attach the exhaust adapter a to the blower plate b with the two tapping screws provided. Make sure that the damper c swings freely.

Fire hazard! Correctly install the vent fan before use.
When changing the vent fan position for wall venting or roof venting:
Properly align the ventilation fan openings and blower plate knockouts.
Ventilation fan openings should be completely exposed to the outside.
After installation, check the air ventilation path. Refer to step 2 for proper vent selection.
Improper installation can cause problems such as:
Inability to assemble the blower plate or ventilation motor correctly
Abnormal noise during product operation
Weak ventilation
Product overheating and the possibility of product breakdown or fire