where can I upload my National Financial Services 1099-DIV on my amended tax return

Here is how to amend your return and add the missed 1099-DIV:

1. Log in to your TurboTax Online account, choose 2024, then Amend 
2. Answer the first few questions, then select your reason for amending.
3. Navigate to Federal Taxes in the upper left, then Wages and Income.
4.  Add or Edit Investments and Savings (1099-B, 1099-INT, 1099-DIV, 1099-K, Crypto) > Add/Edit
5. Choose Add Investments
6. Choose "Enter a different way" 
7. Select 1099-DIV and continue
8. Either upload or choose "Type it in myself"
9. Enter the information from the 1099-DIV requested in the interview

When you start to amend your return, your refund or tax due will be $0. After you add the 1099-DIV, it will increase to the new amount due.

Here is some information you may find helpful: How to File an Amended Tax Return with the IRS