The chain on an electric chainsaw needs to be sharpened regularly and tightened properly. On occasion, you will need to replace the chain, either to have it sharpened or because the teeth or depth guides have worn beyond the point of being usable. Improper installation of the chain could keep the saw from cutting properly or worse, could be dangerous.
Disconnect the electric chainsaw from power.
Loosen the two nuts holding the bar onto the saw by about half a turn.
Loosen the tensioning adjustment screw with a flathead screwdriver. Turn the screw counterclockwise until it will not turn any longer, which will loosen the chain considerably.
Remove the two nuts holding the bar cover onto the chainsaw with the wrench.
Remove the chain from the bar and clutch sprocket. Remove the sprocket guard if your saw is equipped with one.
Place the new chain onto the bar and clutch sprocket. Be sure that the teeth of the new chain are pointing forward when on top of the bar.
Replace the sprocket guard. Hand tighten the two nuts that hold the bar onto the saw.
Turn the tension adjustment screw clockwise while holding up on the tip of the bar. When the chain is tight, tighten the two bar nuts with your wrench.
The tensioning adjustment is a single screw found on one side of the bar at the point where the bar meets the saw. On most chainsaws, the tensioning adjustment screw is found on the motor side of the bar. To check the proper tension on the chain, lift the chain on top of the bar out of the trench in the guide bar. You should be able to pull the bottom of the chain guides just about even with the edge of the bar. If you can pull past the bar, the chain is too loose. If you cannot pull the chain so that the guides are at the edge of the bar, the chain is too tight.
When working with power tools, wear appropriate safety gear, including safety glasses.