I drove for a delivery service, Postmates. What form do I use?

[AnnetteB6]

As an independent driver for a delivery service, you would enter your income on Schedule C for business income and expenses and claim any expenses that you had related to the work you performed.  If you received a Form 1099-MISC showing your income, you would enter it into your return, otherwise you can report your income as 'cash'.  

See the following TurboTax articles for more information:  

Am I considered self-employed?

How do I report income from self-employment?

What self-employed expenses can I deduct?

@jeriwhaley