How do I use form 1098 T when its in my Childs name?

You just enter his 1098T on your return. Because the student is your dependent, you are allowed to claim the credit, which means you must enter the 1098-T, on your return. 

The 1098-T is only an informational document. The numbers on it are not required to be entered onto your or your student's tax return. However receipt of a 1098-T frequently means you are either eligible for a tuition credit or possibly your student has taxable scholarship income. 

If you claim the tuition credit, you do need to report that you got one or that you qualify for an exception (the TurboTax interview will handle this)