Form W-7, Application for an ITIN cannot be electronically filed with the taxpayer's tax return. The IRS requires that the form be mailed with the tax return, proof of identity, and foreign source documents to:
Internal Revenue Service
Austin Service Center
ITIN Operation
P.O. Box 149342
Austin, TX 78714-9342
After processing, the IRS will issue the taxpayer an ITIN through the mail.
Additional Information:
IRS.gov - How do I apply for an ITIN?