I think you can do this by means of the "Custom Payload" option in the fulfillment section of a page.
You first need to access a page which allows a fulfilmment, then you click on 
Once in the window of the fulfillment you may select add dialog option and then custom payload 
Finally, you can use Google's documentation to build your custom payload of type "button" and paste the code in here. This is a link to the documentation section I'm referring to.
On a final note, please try to solve the problem by yourself: it is the second question of yours I answer on this topic, and in both cases a simple Google Search provided all the information needed.