Assuming the 1098-T was for an amount billed, but not paid; you do nothing. Do not even enter the 1098-T. The 1098-T is only any informational document. The numbers on it are not required to be entered onto your tax return. This further assume, you did not attend classes in 2017.
Assuming you paid tuition in 2017;
You have a choice (actually a tax loop hole). You can claim nothing on your 2017 tax return, since it will be reimbursed in 2018. Or, you can claim a tuition credit, because you are out-of-pocket.
It may get a little complicated reporting the 2018 reimbursement correctly. It's best explained by example. Lets say you paid $6000 in tuition, in 2017, and use $4000 of that to claim the tuition credit ($4000 is all you need to get the maximum amount of credit on the American Opportunity Credit).
In 2018 you employer reimburses you $6000. On your 2018 W-2 (received in Jan 2019), he shows $5250 (the maximum allowed) of tax free educational reimbursement and $750 of taxable reimbursement. $750 will have already been included in box 1 of your W-2 as taxable income. You now have to report $3250 (4000-750) as additional taxable income on your 2018 return. $3250 goes on line 21 of form 1040 as "Taxable Reimbursement". TurboTax can not automatically pull that from your w-2. You have to enter it manually. In TurboTax enter at::
Federal Taxes Tab
Wages and income
Scroll down to:
--less common income
---Misc Income, 1099-A, 1099-C..... (Press start)
----On the next screen, select Other reportable income
-----Two screens in, type Tuition reimbursement and $3250
Alternatively (using the numbers in the example), you can use only $750 to claim the tuition credit in 2017. Then, you will have to do nothing with your 2018 return.