If you already filed and forgot to include your education expenses, you'll have to file an amended return (1040X) if you want to include them. But you'll need to wait until IRS has processed your original return and issued any refund. Then you can prepare the amendment in TurboTax.
IRS only accepts the 1040X on paper, so you'll print, sign, and mail it.
Here's a link to the TurboTax support page for amending returns, which will get you started: https://turbotax.intuit.com/tax-tools/tax-tips/IRS-Tax-Return/Amending-Your-Income-Tax-Return/INF120...
