First thing you should do is to prepare the backend - create the child theme. It will be very useful whenever you decide to tweak something in your theme.

The thing is, if you add some code to original files of your theme and you'd receive and update to the theme, then all your code would be lost.

So don't skip this step and create the child theme! I've used and recommend tutorial by tutorial by PhoenixFlame

Have you already created the child theme? Great! Lets add some button(s) :)