I already filed my 2020 taxes, I have 2 children, will I receive the expanded child tax credit that is part of the stimulus bill? If not, how do I get it?

The expanded Child Tax Credit has not yet been enacted into law.  However, the current draft bill calls for it to become effective with the 2021 tax year (returns filed in 2022). So we don't know yet.

Thanks for your reply. In a NYtimes FAQ it says something about receiving an advance on this. I paste the answer below. How does this work?

You could receive some of the credit as an advance on your 2021 taxes.

The bill would make the credit fully refundable, which means you can receive money from it as a tax refund even if your tax bill is reduced to zero. And half of that money could be advanced to households over the next six months (based on their 2020 tax information, or 2019 if that was unavailable). It’s not clear how frequently payments would be made — perhaps monthly — but under the bill they would begin in July.

The changes are effective for 2021 only, though at least some Democrats would like to make it permanent.