Enter your W-2 income only as your business income. It should be on the screen Tell us more when it asks Total income earned at this job. Your Percentage of income earned using this home office should be 100% since this is your only place of work. See screen shot attached.
You should be going through the interview for "Employment Expenses" under All tax breaks (below Your tax breaks) under the Deductions & Credits tab at the top (see screen shot attached). Make sure you are not in the self-employment area.
