Into the Before Body section of custom code.
Then in the design view, copy the code that was in the Before Body section of custom code previously, into an html embed widget. You can give the html widget a class, and give it padding, margin etc.:
Copy to html embed widget:
div class="as-track-button" data-support="true" data-width="280" data-size="large"></div>
Notice there is some data-width property there and data-size property from the aftershift code.. you might want to change that, depending on your design, or just leave it alone...
Once you do these changes, then publish, and you can see, the box aligns how you want it (although in your design, you might put it somewhere else, or change the look of the html embed widget):
Hope that helps you, cheers !