Fed Return finished but found I need to add dividends on line 3b 1040 and line 3a to 1040; how do I get back to the forms to make these changes???

I need to change my 1040 and add dividend amounts to lines 3b and 3a.d. I do not know how to make these changes since I had the tax forms printed for my review.  How do I make these changes to my tax returns before filing manually, not electronically. 

I did not see any way of getting back into the forms in order to make these changes and discovered them on the actual printed form where they were left out.