The address to send your Federal Tax return depends on where you live and if you are getting a refund or making a payment with the return.
Here is a link to the IRS website and the addresses of where to file Where to Mail your tax return
Find the state you live in in the first column and then if you are not making a payment use the second column address.
If you are making a payment use the 3rd column address.
To mail your state return please search for your state Department of Revenue or contact your state by phone for the address.
You can mail in your returns once you have completed them. However, the IRS will not begin processing paper returns until January 27, 2020. Be sure you have received and input all relevant information and documentations such as forms W2, 1099 and 1098 as applicable.