In newer versions of software, first go to the Start menu at the top of software window. Next, choose "Couple Returns (2to1)". A window will pop up allowing you to locate the two returns you wish to couple. Simply find the first and second returns by clicking on the "Browse" buttons. When you are done click "Finish" and a coupled return will be generated for you.
In older versions of software, choose menu "Start | re-couple tax return", and choose the two single-return files for re-couple.