If child graduates college in spring and attends masters program in fall how do I claim the graduate expenses but not the masters?

If the student is your dependent, you can claim ALL the expenses, no matter who paid them.

I am not clear if the student had finished the first four years before 2020. If the student was still perusing a degree in 2020, you might be eligible for a credit based on all the expenses paid. 

According to the IRS:

“Q9. If a student was an undergraduate student during the first part of the tax year and became a graduate student that same year, can the student claim or be claimed for the AOTC for the qualified tuition and related expenses during paid during the entire tax year?

A9. Yes, AOTC can be claimed for this student for qualified educational expenses paid during the entire tax year, if all other requirements are met and the student:

• Has not completed the first four years of post-secondary (education after high school) education as of the beginning of the tax year, and
• Has not claimed the AOTC for more than four tax years.”

IRS Link

You enter only the 1098-T and expenses  from the undergraduate school.