Retirement tax questions

This is still rather confusing, I am trying to determine how Turbo Tax knows if the amount on the SSA-1099 is regular SS income or  Disability SS income. In my case, mine is regular SS income, while my wife's is disability SS income, we file jointly. Where in Turbo Tax do I let the program know about the disability aspect of my wife's income? I am using the CD/Download version of TT.