Have a 1099-NEC for self-employed income, trying to input. Turbo-tax asks if I "received a tax document from my payment processor." What ? How to input?

That would be referencing a 1099-K.  Businesses that accept credit cards for payment may receive a 1099-K for the reportable transactions they processed on your behalf.  If you do not accept credit cards or did not receive a 1099-K, the answer to the question would be "no" but you would enter your total income for your business either way.

If you did receive a 1099-K, please follow these steps to enter it:

1. Open or continue your return
2. Search for Schedule C and select the Jump to link in the search results
3. Answer the questions about your business. On the Let's enter the income for your work screen, select Other self-employed income
   • If you’re returning to Schedule C, select Review or Edit next to your work and then answer the questions about your business
4. On the Tell us about other self-employed income for your work screen, enter your 1099-K info
5. Select Continue when finished

If you are entering income from a 1099-K, remember that it reports the gross amount of the transactions. It doesn't include any adjustments for credits, refunds, discounts, or fees. You’ll have a chance to enter self-employment expenses in another part of your return.

See Understanding Your Form 1099-K for more information about why you did or did not receive a 1099-K.