its simple. the tv has mounting holes on the back. get 2 3+ foot long boards. 1x4"s would probably work better. drill holes in the boards that match the mounting holes on the tv. then mount the boards to the tv.
on the back of the cabinet where those 2 boards would come down to. look for solid wood. (if there isn't any, add more boards to the back). hold the tv where you want it. then have a buddy drive screws to join the boards to the back of the stand.
i could do all this in less time than it took me to type this.