ITIN

You can file Form W-7, Application for IRS Individual Taxpayer Identification Number (ITIN), with your federal income tax return. You must also include original documentation or certified copies from the issuing agency to prove identity and foreign status.

If you qualify for an exception, then file Form W-7 with your proof of identity and foreign status documents and supporting documentation for the exception.

Option 1
Apply for an ITIN in-person using the services of an IRS-authorized Certifying Acceptance Agent. This will prevent you from having to mail your proof of identity and foreign status documents.

Option 2
Make an appointment at a designated IRS Taxpayer Assistance Center. This will also prevent you from having to mail your proof of identity and foreign status document 

After processing, the IRS will issue your ITIN through the mail.

Websites for reference: 
HOW to get an ITIN
Certifying Acceptance Agent
Taxpayer Assistance Center