I already filed my taxes and forgot to add a 1098-T. I know i have to amend my return but on my account it doesnt have that button.

To access your current or prior year online tax returns sign onto the TurboTax website with the userID you used to create the account - https://myturbotax.intuit.com/

Scroll down and on the section Your tax returns & documents click on Show.  Click on the Year and Click on Amend (change) return

If your returns were e-filed today and you filed both Federal and state returns, you'll need to wait until both of returns are completely processed before you are able to start an amended return.