I sold real property on a land contract this year. I receive monthly payments. How do I report the monthly interest income I received during this year?

So if you have an installment sale you report the interest and principle on the form 6252 and the interest will be carried to the Sch B automatically.  Did you fill in the 6252 yet ?  

 

If you  reported the entire capital gain or loss in a previous year (rather than reporting as an installment sale each year), there is an alternate way to enter the interest, for this year.  Enter at the 1099-INT screen, even though you didn't actually receive a form 1099-INT.

 

In TurboTax (TT), enter at:
- Federal Taxes tab (Personal in  Home & Business)

 - Wages & Income

Scroll down to:

-Interest & Dividends

  -Interest on a 1099-INT