Should I provide home office expenses for the full year even if I started my business in September?

I registered my business in September 2019. I have expenses for 2019 but no income until 2020. When I report my home office expenses (heat, internet, etc.) in TurboTax, should I report using 12 months of expenses or just 5 months? Where can I indicate that my expenses are only for 5 months of the year?