First of all, the employer has to have the W-2 finished and available. Many employers at this point in time may not have it yet available since they have until January 31.
Some employers or payroll providers have them available at their own website. You can ask your employer or payroll provider if they offer that service. Do you remember if you went to your employer's website or a payroll service website (if applicable?)
Or did you use the W-2 import feature built into TurboTax? If your employer or payroll provider partners with TurboTax for W-2 importing, here's how it's done in Online TurboTax:
https://ttlc.intuit.com/community/entering-importing/help/how-do-i-import-or-enter-my-w-2-in-turbota...
