Under Dashboards, click on Edit from the top-hand navigation.
To add a document, click on the Pencil next to the section header of your choice (in the Playground client, we use the Documents section as an example.)
You can customize the Section Heading name as well as the Section Description.
Click the Add New Visualization button below the existing Visualizations section.
Update the Name and Description.
Update the Type of visualization.
If you do not see the Type that you need, click Google Sheets/Docs and add the Embed Code to the box underneath the dropdown. Any applications that have an embed code (such as PowerBI) can be pasted here.