If I paid for some of my brother's tuition, where do I add that expense?

Unless you claim your brother as your dependent, you cannot deduct his qualified educational expenses. 

Otherwise, your expense is considered a gift which is not deductible.

To be deductible, the school must be a qualified educational institution.

An eligible educational institution is generally any college, university, vocational school, or other postsecondary educational institution eligible to participate in a student aid program administered by the U.S. Department of Education.

See Rules For Claiming Dependents

 To enter educational expenses:

·        Type in 1098-t in the search box, top right of your screen, then click the magnifying glass

·        Click the jump to 1098-t link in the search results

·        Follow to prompts and online instructions