First of all go to the Master Vault. If you know which locker the document it in then click on that locker. If not you can find the document that you want to delete by using the search function at the top left and typing in the file name or look in one of your lockers where you have stored the document.

Click on the document and then click "delete".

You will see that the deleted document is now in the "Trash" where it will remain for a period of time before deleting permanently.

If you click on "Trash" on the side bar you can view the documents that you have deleted and either delete them permanently or restore them.

If you wish to delete multiple documents at the same time, you can select them by checking the tick box in the bottom right of the document and then clicking the delete button on the left. Again, the documents will all move to the trash where you can delete them or restore them.