At the end of the day, all you're doing is telling Marketo that when someone clicks on the button image, they're taken to the web address you store in the token you've made.
It would look something like this:
Double-clicking for Details would reveal the rich text editor, where you would then put your web address:
In the email editor, you'd then set the button's destination address to the token "{{my.resourceURL}}". The behavior takes leads who click on the button image to the address you specify in the token:
Hope that helps to address how you use tokens!