I have job related expenses (mileage, office supplies etc) do I put these expenses under "business income & Expenses" secion or under employment expenses in the deductions section? not sure why there are two places for similar expense reporting

Where you enter this expenses depends on if you were an employee or self-employed. If you were an employee and have unreimburseable employee expenses they are reported on Form 2106. If you were self-employed the expenses would be reported in your Schedule C along with your business income.