doc: Fix the instructions to securely delete a persistent storage.

wiki/src/doc/first_steps/persistence/delete.mdwn

@@ -17,12 +17,18 @@ the same USB stick without having to reinstall Tails.
 <strong>This technique may not prevent an attacker to recover the files of the
 old persistent storage using [[data
 recovery techniques|encryption_and_privacy/secure_deletion#index1h1]].</strong>
-For more security, you can do the following operations on the USB stick:
+For more security, start Tails from another media, and do the following
+operations on the USB stick that you want to delete securely:
 
 <ol>
-<li>[[Erase Tails|resetting_a_usb_stick]]</li>
-<li>[[Securely clean all the available disk space|encryption_and_privacy/secure_deletion#index4h1]]</li>
-<li>[[Reinstall Tails|usb_installer]]</li>
-<li>[[Create a new persistent storage|persistence/configure]]</li>
+<li>[[Create an encrypted partition|encryption_and_privacy/encrypted_volumes]]
+on the whole USB stick. This step erases both Tails and the persistent storage
+from the USB stick.</li>
+<li>[[Securely clean all the available disk
+space|encryption_and_privacy/secure_deletion#index4h1]] on this new encrypted
+partition.</li>
+<li>[[Reinstall Tails|usb_installer]] on the USB stick.</li>
+<li>Start Tails from the USB stick and [[create a new persistent
+storage|persistence/configure]].</li>
 </ol>
 </div>