Here's what happened:
* James and Lily were in their home, hiding with Harry. They knew Voldemort was coming, as Peter Pettigrew had betrayed them.
* Lily begged Voldemort to spare Harry. She offered herself in his place, and Voldemort agreed.
* Voldemort entered the house and killed Lily. He then went to kill Harry, but the love Lily had for Harry protected him.
* The killing curse backfired on Voldemort, leaving him weakened and without a body.
There is no mention of James putting his wand on the couch in any of the books or movie adaptations. He would have been actively defending his family against the attack.