Awesome, thanks for posting this here, and welcome to the forums! 
All of the steps you took are correct, what’s missing is the next step of adusting the Parent Offset and Child Offset attributes on the Distance Constraint. These determine what relative position on the parent and child respectively to constrain together.
Per default, the center of the parent and child are constrained. But in this case, since we are talking about a 2-point muscle constraint, you’ll want to instead constrain the tip of the muscle to the surface of the parent, the head in this case.