How to implement code, for example for the Facebook Login Button?

I would like to offer Facebook login on my app. Now, I could simply create a blue button, but Facebook offers (and I think, insists on) a very professional looking button - you probably know it:

Now I can easily get the code from this site:

But how can I implement that code? Where can I upload it so it shows the button in the right place with the correct design etc.?