Interest only mortgage expenses

I rent out my only property and am living in rental property myself. I am a full time student. I pay mortgage interest on the property I rent out and it is an 'interest-only mortgage'. My mortgage payments are ~ equal to the amount I receive in rental income and as such I do not make profit from renting this property out. How do I input the mortgage expenses into a tax return self assessment as I cannot find where and how to input this. I have watched a lot of the videos available and non of them seem to cover interest only mortgages.

Hi,
The mortgage is declared in the section for residential fainance costs - its on the last page of the rental section in the online return. for paper returns it is box 44.
Thank you.