Thanks manActually, that one looks like it clips on to the plastic AM4 brackets. It can take a little bit of force to get it on there.
If your problem is missing the two plastic brackets, well, you can get replacements. Though it would be easier to return that cooler and get something that comes with it's own mounting hardware.
I don't necessarily vouch for the below. Also seem to be people selling original AMD ones on ebay.
https://www.amazon.com/mounting-Bracket-Socket-Heatsink-1-Pack/dp/B07L1Q3XDS