How to enter interest income without a 1099-int?

You can [Edit] or Add the 1099- INT by following these steps.

Under Federal

1. Select Wages & Income
2. Scroll to Investments and Savings (1099-B, 1099-INT, 1099-DIV, 1099-K, Crypto)
3. Click Add/Edit
4. You will see previously entered 1099s
5. If you already have it posted
   1. Select the 1099-INT you wish to edit 
   2. Press the down arrow
   3. Select [Edit]
6. If it isn't posted [+Add Investment]You can [Edit] the 1099- DIV / INT by following these steps.

You still enter it at the 1099-INT screen, even if you didn't get an actual 1099-INT.  It's important that federal interest be entered in box 3, at the 1099-Int screen, in TurboTax (TT).