I accidently selected 'no one can claim me as a dependent', I would like to change this because I can still be claimed as a dependent. Am I able to amend this somehow?

After you receive your full refund - in approximately three weeks (longer if you have an additional child tax credit or earned income tax credit), you will need to amend your tax return, by filing Form 1040X.  To do this, you will log back into TurboTax and select the option "I need to amend my tax return."

You can find more detailed instructions on that process here: How to amend a tax return in TurboTax.

The return on which you should be listed as a dependent will need to be filed by mail, it will be rejected by the e-File system.  You may want to warn the person (or persons) who are claiming you so they won't be surprised by this.