Go to Resources.

Select the Resources tool from the Tool Menu of your site.
Select one or more items, and then click Move to Trash.
To remove a Resource file or folder, select the item(s) by checking the boxes next to each one to be removed, and then select Move to Trash.
Note: Alternately, if you are removing one item at a time, you may select Move to Trash from the item Actions menu instead.
Items are removed.

Note: If you remove a folder, all of the items inside the folder are also removed.