My son received a 1098t, Not sure how to enter it because it is a full scholarship. Box 1 and box 5 are filled out but it is giving us a 418 credit on our taxes.

The credit is 100% of your qualified expenses on the first $2000.  If you spent $418 on books, you get a $418 credit.

But, be aware that you probably can get more. 

There is a tax “loophole” available. The student reports all his scholarship, up to the amount needed to claim the American opportunity credit, as income on his return. That way, the parents  (or himself, if he is not a dependent) can claim the tuition credit on their return. They can do this because that much tuition was no longer paid by "tax free" scholarship.  You cannot do this if the school’s billing statement specifically shows the scholarships being applied to tuition or if the conditions of the grant are that it be used to pay for qualified expenses.

Using an example: Student has $10,000 in box 5 of the 1098-T and $8000 in box 1. At first glance he/she has $2000 of taxable income and nobody can claim the American opportunity credit. But if she reports $6000 as income on her return, the parents can claim $4000 of qualified expenses on their return.