If you are using TurboTax online,
one of the first few pages will ask you if “Who are you preparing this return
for?”. Select “Myself”, then continue on. A page further down the line will ask
for your marital status. If you choose “Married” or “Common Law”, it will then
ask “Do you want to prepare your returns together?” on the next page. There you
will say “No”, so that you can create a return only for yourself.
To
create a return for your spouse, click on “Tools” in the black menu in the top
right, and select “Return Manager”. You can create a new return by scrolling to
the bottom of the list and clicking "Continue" next to "Start a
new 2017 return". Then do the same as you did above.