How to indicate my 18 year old daughter is a full time student. It's not showing a screen where I can indicate it.

Until a dependent is 19 that indication is not needed. 

My return was rejected because she wasn't 17 and under.  Turns out I had to go to extra Income and Credits and go to Education section and enter her expenses and there it indicates which child the school expenses are for and there it indicates she is full time.  I had to dig very deep to find the answer. But thanks anyway.

OK ... so you had a 1098-T from the college and you needed to enter it in the education expenses section of the Deductions and Credits section ... your question said nothing about a form 1098-T or I would have told you where to find it.