1990 190E 2.6 with CHECK ENGINE light on, which came on after car shut down after driving, perhaps due to losing electrical power.

Car seems to drive fine, idle normally (as before), no puttering sounds. By the battery is that black box with a LED light and numbers next to holes. I have never read codes before and this is a bit intimidating. My search shows that I should press the button and hold for 3-4 seconds. The rest makes no sense to me as far as number of blinks the LED makes. Could someone tell me how I can read the code and cancel the CEL in layman's terms? Thanks.