Any job-related expenses for a W-2 employee are taken as misc itemized deductions on Schedule A. So in order to get the home office deduction, you have to be able to itemize, and the misc deductions have to surpass 2% of your adjusted gross income before you'll see $1 of deduction.
If you're not already itemizing, the odds are probably slim that adding a home office is going to surpass the standard deduction of $6300 single/$12,600 married filing jointly. Particularly so if you have few deductions that you even could itemize. Frankly, I wouldn't worry about it.
If you choose, you can always set up the home office in TurboTax and enter the various expense figures, and TurboTax will take the larger of the standard or itemized deductions.
As for prior years, the only way to change a tax return is to file an amended return (1040X). In your situation -- unless you were able to itemize in 2015 -- it's probably not worth your time.
