I got a 1099 nec form because my employer at the time didn't do tax forms right away. How do I handle this on my 1040

Your  should not have received a 1099-NEC as an employee.  It should be reported on a W-2 as it is employee compensation.  

You will need to contact the employer and ask for a W-2 instead of the 1099-NEC. If they will not, then you would need report the income by selecting the following:

1. Income
2. Miscellaneous Income
3. Other Income not already reported on a Form W-2 or 1099
4. Yes, to did you receive any other wages
5. Continue through until you get to Any Other Earned Income and select Yes
6. Select Employee compensation that was not reported on a W-2
7. Continue through answering the questions.  Put a checkmark in the box that says you received a 1099-Misc
8. Select letter H- I received a form 1099-NEC that should have been submitted on a W-2

TurboTax will then include form 8919 with your return for uncollected Social Security and Medicare wages.  This will have you pay 7.65% instead of 15.3%.  

Subcontractors vs employee