My father has passed away and was not the best at computer stuff.

My father has passed away and was not the best at computer stuff.  

He evidently has some errors input in his family tree which is not complete at all.  How do I gain control of his tree information so I can correct it?  My relatives in Norway say they can not access the corrections either.  I must gain control of my dad's family tree with no password or computer now.  He passed away this past summer.  How do I do it?