Did you see this FAQ? How to enter self employment expenses
Are these expenses from a business you own or expenses you were not reimbursed for?
If you own the company most likely it will be filed on a Schedule C with the 1040
If it is an LLC or LLP with more than one owner (not related) it will be a 1065 which you will get a k-1 from
If S Corp an 1120S is filed and k-1 from company
If it is expenses for job but you were not reimbursed it is deductible but only if you itemize deduction