Before beginning, generate the code required to implement your button: see here for info (part 1).
Login to your to your GoDaddy account.
Navigate to the page you want to add the widget to
Click "+ Add new section"
Search for "HTML" in the search bar, then click "Add"
Add the full code (all parts) in the "Custom Code" section, then click "Done"
Place your widget where you want it to be
Preview your page to test it out
GoDaddy does not allow the widget to display normally (i.e. the widget window is limited by GoDaddy's element dimensions). For this reason, we recommend selecting the option "Use as popup" (add "usePopup: true" under the API key in the body tag) to avoid this issue.