How to reset Check Engine indicator lamp

[azurite300E]

I just replaced the missing o2 sensor in my 1986 300E, but the Check Engine lamp still comes on (and stays on) after the ignition key is placed in the ACC position, and won't extinguish even after the engine is started. I'm guessing the error that was stored due to the missing o2 sensor still causes the lamp to stay on and needs to be cleared.

Can anyone tell what the procedure would be? I'm very electronics literate so don't worry about getting technical with this one. Thanks.

-Alex