How do I claim my son in order to receive a refund for him cause I check and am eligible for tax refund for him

Dependents are entered in My Info on your tax return.  Was your son born in 2020?  You need his Social Security number.

Children born in 2020 were not included in the 1st stimulus because those checks were based on 2018 or 2019.  But on your 2020 tax return you can claim your child born in 2020 for the stimulus money, as well as the other child-related credits.  When you go through the screens in My Info make sure to say your child lived with you the WHOLE year.    

The stimulus check is an advance on a credit you can receive on your 2020 tax return.  If something went wrong or you did not get the stimulus check this year, you can get it when you file your 2020 return in early 2021—if you are eligible.It will end up on line 30 of your 2020 Form 1040.

https://www.irs.gov/newsroom/economic-impact-payment-information-center-topic-j-reconciling-on-your-2020-tax-return

https://www.irs.gov/coronavirus/coronavirus-tax-relief-and-economic-impact-payments-for-individuals-and-families

https://ttlc.intuit.com/community/tax-topics/help/how-will-the-stimulus-package-impact-me/00/1393859

At this point, we do not know yet what the new stimulus bill will mean in terms of changes to the 2020 Form 1040, software programming, software updates, etc., etc.  Do NOT be in a hurry to file your 2020 tax return until more is known. Give some extra time to the IRS and the software programmers so that the software can handle the new 2nd stimulus, so that you can get it all by filing ONE time.   It is never a good idea to file early, and it would be especially foolish to file an early 2020 return.