Turbotax does not support form W-7. You will need to prepare it and attach it to your mailed return. Efiling is not possible. Follow Turbotax filing instructions and use a mailing method whereby you can track the return.
you'll find the form and instructions here
https://www.irs.gov/site-index-search?search=w-7&field_pup_historical_1=1&field_pup_historical=1
