Add a new notice.

Select File / Media from the notice type dropdown.

You will see an Add from Media button appear, click it. This opens your media library where you can use a pre-uploaded document or upload a new document by either dragging it in from your desktop or uploading it using the upload tab.

Once you have your document selected click the Insert into notice button in the bottom right of your media library.

Complete the remaining general steps to publish your notice - App Category, App Options, and Publish.