Customize Button

I am presently using this dawn theme a fork from an older version. I currently created a button using the + button and added a button with an embedded link, and it looks like this:

How do I create a customized button with this python logo (link to website here) and have the hover color change in CSS?

I am not a CSS expert, Can anyone help with the CSS code, where to place this css class element, and how to use it as a replacement for the default pink color button? Would be grateful for any assistance with this issue.

Best Regards