Yes. Mail it. If you are getting a refund there is not a penalty for mailing it after the deadline. If you owe tax due, you will be billed by the IRS for the penalty and interest owed for filing late.
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 received the return.