How can I integrate Facebook Share with my website?

I would like to know how can I integrate a Facebook share button in a website so that after someone shares the link, something happens, e.g. some permisson is granted or a premium feature in the website is enabled for the person who shared.

Basically, I want to know when someone shares the link and who did it, so action can be done.

I am sorry if the answer is in the internet already, I couldn't find it.