How do I report a home office for my W-2 income? How do I assess what I can deduct for working from home?

I have entered my W-2 info under Personal/Wages and Salaries, but I do not see where/how to add info that work from home.  I have worked from home all of 2015.  I have the qualifying space that is set up with computer, printer, filing cabinet and is used exclusively for my W-2 job.