Turn the black round knob on the power head shaft bottom counterclockwise to loosen the coupler.
Pull the top cover straight off of the brush cutter attachment shaft. Push the button in on the brush cutter attachment and slide the upper shaft into the bottom of the power head shaft.
Rotate the brush cutter so that the button seats and locks in the hole in the shaft. Turn the coupler knob on the power head shaft clockwise to tighten it.
Put on safety glasses.
Place the trimmer on a bare, flat surface. Press the primer bulb 10 times to add fuel to the carburetor. Set the choke on "Full Choke." Squeeze the throttle trigger and pull the starter rope until the engine starts and then dies.
Turn the choke lever to the "Half Choke" position. Pull the starter rope until the engine starts.
Pick up the brush cutter and hold it on your right side with your left hand on the front handle and your right hand on the rear handle. Guide the cutting blade left-to-right to cut large weeds and brush.
Press the "Stop" switch to turn the brush cutter off.