Your documents are stored in your "My Files" section. Click "My Files" on the left side of your screen and you will see a list of your documents. Hover over a filename and you will see three dots to the right-hand side of the screen. Click the three dots and select Delete.
Once the document has been deleted you cannot retrieve the document. However, if it is a document that you have created through a SmartGuide Interview, you can recreate the document. Click SmartGuide Interviews on the left side of the screen, select the document you want to reassemble underneath, and click "assemble". Your document will be reassembled and placed into your "My Files".