To upload a file
Currently the best way access your site's file folder is to go through the link editor of the Builder.
Highlight some text in a title or paragraph module and click the Link button in the formatting toolbar.
In the Change Link popover click Upload File to upload the file of your choice.
Once the file is uploaded, it is not necessary to proceed with the link creation process. Click Remove in the Go To Link popover once you return to the Builder.
The location of your file will always be your site name/the file you uploaded, as seen in the image above.
To delete a file
From the File tab of the Change Link popover, hover on the file you wish to delete. A red x will appear in the lower right. Click the x and confirm you wish to delete.
IMPORTANT: Make sure none of the files you are deleting are in use on your published website, otherwise this will result in broken links.