Already filed taxes but I am a student and didn't hear about student credit

If you are being claimed as a dependent on anyone else's tax return, you are not eligible for education credits.

https://www.irs.gov/help/ita/am-i-eligible-to-claim-an-education-credit

If you parents didn't pay more than half of your support and you don't qualify as a dependent on their return, you can report the 1098-T on your return and claim the Education credit. 

If you already filed your return but you qualify to claim the 1098-T, you need to amend your return to make the changes.

If your return is accepted, wait until your return has been fully processes and you received your refund ( if you are expecting a refund ), then amend your return. 

Here's how you amend your return:

1. Sign in to you account.
2. Scroll down to Your tax return & documents , select 2019 and then Amend (change) return. 
3. Select Amend using TurboTax Online.
4. Follow the instructions, your refund or tax due will change to 0. This is normal on amended returns.

Amended return can't be e-file, you need to print it and mail it in.

On the Tax Home web page when the Form 1040X for amending a 2019 tax return becomes available there will be a link - Amend (change) return.