For a federal return:
https://www.irs.gov/filing/where-to-file-paper-tax-returns-with-or-without-a-payment
When you mail a tax return, you need to attach any documents showing tax withheld, such as your W-2’s or any 1099’s. Use a mailing service that will track it, such as UPS or certified mail so you will know the IRS/state received the return.
If you are mailing a state return, then it goes to a different address--you do not mail federal and state returns together. You have not mentioned your state so you may need to look up the address for mailing your state, although when you print your returns for mailing the addresses should print out with the mailing instructions.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**