Do I need to file two separate returns if I worked as self employed (1099-C) for one month in 2022 and then had a W2 the remaining months? How can I file my taxes?

No.

You do not file two separate tax returns.

You report all your income (both from the 1099-NEC and the W-2 on the same tax return).

The form W-2 is entered in the Job section.

In TurboTax, you can enter your form W-2 by following these steps:

1. In TurboTax, open your tax return
2. Click on Federal in the left-hand column, then on Wages & Income 
3. Continue to All Income and locate the section Job (W-2) and click on Start.

To enter your 1099-NEC, follow the instructions in this TurboTax Help article.

You’ll need to use TurboTax Deluxe (or TurboTax Self-Employed if you have expenses to deduct), or TurboTax Home and Business.

You can read this TurboTax article for more information.