Receiver and dvd

I can not get sound from the receiver to the TV and DVR they were working ok but I must have pushed buttons and have done a boo bo my son put everything to gether and we do not have any books as it was his to start with and I can not contact him at this time please can some one taalk me through putting the buttons back in the right place. I get pitcures with DVR and TV but no sound please help Cheryl McMahon
I do not know the products numbers I will make a guess as it will not let mme pass my problem to you