How to implement a sign in button



I have a very basic question. I would like to implement a sign in button on my website.

How to do Implement the button? Is there predistinguished HTML to use the button? can I use any button and just set an action to in order to get to the “Authorize x To Your Account?” screen?

The flow is described here, I know what I’m trying to do is doable, it’s done all over the place. I’d like to discuss this with someone but it seems no one on the web knows how to do this and I’ve been searching for 2 days.