Freelance work is self employment and therefore should be reported on a Schedule C as business income. Since you stated that you have performed this type of work for numerous different companies in various states, provided the type of work performed is generally the same industry-type work, all income regardless of what State, can be reported on the same Schedule C in TurboTax.
Please follow the instructions here to enter your income onto your Schedule C:
How Do I Report Income From Self-Employment
Reporting Self-Employment Business Income and ... - TurboTax
