If you were a dependent on another tax filing or if your AGI was too high on your 2019 filing you would not have been eligible for checks. On your 2020 filing if you no longer are a dependent to someone else or your AGI is less than 75,000 you are eligible for the checks as the stimulus is based on 2020 data.
Yes, @palmax is correct. The Recovery Rebate Credit is the way to receive any eligible stimulus payments that have not yet been received.
To do this in TurboTax for returns not yet filed, follow these steps:
Click the link for the details on how each stimulus payment is calculated: