If you only have Line 20 Code AE Excess Taxable Income, or Line 20 Code AF Excess Business Interest Income, you are not required to file form 8990 if you are not subject yourself to the section 163(j) limitations. 20 AE and 20 AF are used in your calculations to see if you are subject to the limitations, they don’t carry forward to next year other than in the three year moving average.
If you have Line 13 Code K, Excess Business Interest, then you do need to file 8990. You’ll have to get it from irs.gov/forms and attach it to your printed return and file by mail this year. That’s because Excess Business Interest is the amount your K-1 entity couldn’t deduct this year because it was limited by Section 163(j). This amount is passed through to you, it is not carried forward by the partnership. You have to carry it forward to a future year where the line 20 items above form the same entity can be used to offset that carried forward expense. So it reduces your basis this year, but you get the deduction (hopefully) in a future year.