Wide Fitting Children I Need Help Fitting A Door To An Interior Wall?

I need help fitting a door to an interior wall? - wide fitting children

I put a door to keep the bottom of my stairs to my dogs chewed up the stairs and my carpet. The stone wall outside Lancashire is an area filled with foam and covered with plasterboard. I think that is a child, but the place is not big enough, and can skip directly above. Any tips on how they would fit?