The lab says to type "nano heartbeat". When I do that all I get is gibberish (see attached). I figured out that if you type instead "nano heartbeat.yml" that it opens properly.
Which lab? At any rate, yes, you definitely want to edit heartbeat.yml, not the actual heartbeat binary 
Lab 1.2 in the Engineering Observability Course.
It was just "user error". Just wanted to post in case anyone else does the same thing.