To sign documents you need to open the return. Select the print return Icon. When Print center opens on the left select "EF Signature Forms" on the bottom right side you should now see a Signature pad button. Selecting that opens the Signature widget. In the widget on the left are all the forms that can be signed. on the right is the form and you should see the color-coded fields that can be signed.
Sorry that was for using ProSeries Signature Pad.
The link below is for using E-sig in ProSeries.