My 1098-T form was mailed to me after I filed my taxes can I still add this document even though I received a check already ?

You can amend your return as you may qualify for some education credits. Please click https://ttlc.intuit.com/questions/3061514How do I Amend (Change or Correct) a 2015 Return in TurboTax? for instructions on amending your tax return. 

For instructions on where to enter the Form 1098-T, Please click https://ttlc.intuit.com/questions/2562661 

Amended returns have to be printed and filed by mail. It can take the IRS up to 12 weeks or longer to process them.