This is a nice quick process! Head over to your Dashboard, then navigate to "Media" > "Library" using the menus.
When you're in the Media Library, you will see all of the items you've uploaded to your Edufolio.
First step is to switch the view of your Media Library to "List". To do this click the list icon at the very top of the screen next to the "All media items" drop down menu (shown below).
Your view will now list each upload and show you the "bulk action / selection" column where you can tick a box next to each upload to identify that you want to undertake a bulk action with it.
Next, use the "Bulk Actions" drop down menu and select the "Delete Permanently" option (shown below).
Finally click "Apply" (next to the drop down menu), and you're done!