First of all, your employer or payroll company must partner with TurboTax for the W-2 import process. Secondly, the W-2 must be available for import. Not all companies have them available yet. An employer must provide one by the end of January.
You may need a verification/access code off of your physical W-2 in order to perform the import. You may be able to download a copy of your W-2 to view if your employer/payroll company provides them online for employees to download. It should have the import code on it, if needed.
Also see this FAQ:
https://ttlc.intuit.com/questions/2588751-why-can-t-i-import-my-w-2
