Just had a baby this year and I stopped working in April 2020, how do I add my baby to my tax return this year

just follow the Turbo tax prompts and it will ask you about dependents.  Be sure to answer that the child lived with you ALL YEAR (there is a small note on how to respond for newborns because if you answer with a month less than 12 it is going to mess up)

You will also see the stimulus payments for this child on Line 30 of Form 1040 - it is the last step of the program. 

You should be filing a Joint return with your husband.  Did you file Joint for 2019?  A Joint return is one return combined for the both of you.  Just add her under My Info. Since she was born in 2020 you will say she lived with you the WHOLE YEAR.  Do not just enter the number of months.