I have already filled and have received my refund. If the current bill going through the senate passes and raises the child tax credit how do i receive the difference?

The child tax credit change that is going thru the senate right now is for tax year 2021. If it passes the way it is being presented right now, you would get credits in the form of monthly payments for the last 6 months of 2021, and then you would get the remainder credit when you file next years taxes, not exceeding the $3000 or $3600 total, depending on the child's age. So no need to do anything with your Tax Year 2020 taxes. They should not change.