How do I claim/deduct items purchased in 2018 for a business (sole proprietorship) that was not opened/started until 2019?

I worked in 2018 as an employee for most of the year (so I had income and a W2 for that) At the end of the year I purchased items for a business that was not started yet. (Sole proprietorship opened in 2019) When filing taxes for 2018 how do I deduct items without filing as self employed because for most of the year I was working for a company and didn’t actually become self employed until 2019?

Thank you for all the help. 🙂