thanks… I found it finally on WES website when creating application…
For completed, incomplete and in-progress study, ask the institution responsible for conducting the examinations to attest and send your documents directly to WES.
Send in a Sealed Envelope
If the institution gives you the document to send to WES, the document must be attested, dated, and placed in a sealed envelope that is signed or stamped across the back flap by the appropriate authentication officer at the institution that conducted the examination. If the envelope is opened or there is no stamp or signature across the back flap, WES cannot accept the document.