To delete a folder:
Tap the folder.
Tap Delete Folders icon above the folder list on the left-side navigation panel in two-pane layout.
Tap Delete Folder from the Folder Actions drop-down list above the folder list on the left-side navigation panel in three-pane layout.
Confirm that you really do want to get rid of the folder by tapping OK in the Delete Folder dialog box.
Your deleted folder is now a subfolder inside the Trash folder. If you tap Trash, you'll see it.