To get started, navigate to the services pane on the right side of the app ("+ Add widget" button). Select “Content Widgets” and then the “<HTML>” tile -- you’ll notice that a new widget has been deployed to your dashboard.
Please note: you cannot add HTML to your new widget prior to entering the “Edit Widget Settings” menu and hitting the “Save” button.
Now that you’ve specified your library of choice, you’ll want to start adding your script. To do so, you’ll once again need to navigate to the gear icon at top right of your widget -- this time select the “Add Data” menu. You’ll then be presented with a large text field where you can enter your code. Just be sure to hit the “Save” button once you’ve made your changes!