I believe this option is only available for Proseries Professional users.

As a Basic user, this is what I do:  tag all income items as TP or SP.  Save the file.  Then save the file again, this time as TP Separate.  Set the federal return to MFS, turn off the e-file option for the federal return, and work on the states.  When finished, you can file the states separately

Do the same for the spouse, although you have to manually switch the Spouse and Taxpayer name on the file.