Basically, if you work it through the program you'll have a screen in the rentals section where you can indicate that you are renting the property at below FMRV. Select that option.

What happens is that when your rental expenses (such as mortgage interest and property taxes) gets your taxable rental income to zero, that's it. Any additional expenses that exceed the rental income will not be carried over to the next year. You just lose your carry overs permanently and forever.  Just be aware that when you sell the property in the future, it's gonna hurt you tax-wise not having those carry over losses to deduct from your gain on the sale of the property.

Also, just because your rental income is less than your rental expenses, in no way, form or fashion means you're renting at below FMRV either.

It is extremely rare for rental property to ever show taxable income at tax time "on paper" when you do your taxes. Especially if there's a mortgage on the property.