Can’t attach master link I’m trying to install a chain with a snap on master link, but I can’t figure out how. I’ve tried twisting the chain as suggested by other questions to get it into place, but that doesn’t help. How do you do this? What’s the secret?



It’s a Shimano 8S CN-HG40 chain.
The secret is simple, you need to:  


place the master link (the part with the pins) with the opening towards you, 
bend (flex) the chain so the open ends of the pins come closer to each other, 
put the flat part of the master link, 
release the bend allowing the pins to snap into the flat part of the master link.


Since one picture saves 1000 words, they say...


The bend of the chain is a bit exaggerated, only to show the idea of the action required. One bends the chain using their hands.

And from my own experience - I prefer this type of master link over power link since linking and breaking the chain does not require literally any tools (excepto for one's hands) making it great for road-side repairs. Disengaging power link does require at least pliers (dedicated tool recommended) unless one has enormous strength at their fingertips.