You'll enter them under the Personal tab rather than the Business tab. If you're entering them under "personal," then they are for W-2 employee expenses rather than Sch C self-employed expenses.
Click on Income & Expenses, then Deductions & Credits, then scroll down to Employment Expenses and select Job Expenses for W-2 Income. Then follow the prompts.
You'll eventually come to the screen asking Did you buy or own any items for use on your job. Check "yes" and that will initiate the asset screens for depreciation, where you can tell TurboTax what you bought and all the particulars.