I am self employed and 1 room in my home is an office - I want to take that deduction?

On the Here's your [type of work] info screen, click on Add expenses for this work. Check the box next to Home office and then choose continue. This may be in the recommended expenses section or later in the less common expenses section, depending on what you do. 

Back on the Here's your [type of work] info screen, click the pencil icon to edit your home office expenses. Enter the basic information about your home office to determine whether you qualify for the home office deduction. Continue answering the questions to calculate the amount of deduction you can take on your tax return.

For more information, view our help article Where do I enter the home office deduction for my business?