What do I put in a schedule c if I received a 1099-NEC but am not self-employed?

Why did you get the 1099NEC?  It usually is for self employment.

Yes you are the owner of your own self employment business. You are in business for yourself. Use your own info. The people or company that pays you is your customer or client. You need to fill out schedule C for self employment business income. You are considered to have your own business for it. YOU are the business.

When you are self employed you are in business for yourself and the person or company that pays you is your customer or client.

To report your self employment income you will fill out schedule C in your personal 1040 tax return and pay SE self employment Tax. You can fill out Schedule C and enter Self Employment Income into Online Deluxe but if you have any expenses you will have to upgrade to Premium version. Or buy any of the Desktop programs. All the Desktop programs have all the same forms, but you will get the most help in the Home & Business version.

Where are you stuck on Schedule C?  What are you trying to enter?

How to enter income from Self Employment
https://ttlc.intuit.com/community/self-employed/help/how-do-i-report-income-from-self-employment/00/26653