how do i blend a ragdoll and a characters animation

can you please tell me how to do this. i want it a bit like this https://www.youtube.com/watch?v=NjATj_leMRI my game is a fps and right now all i have is,when a player dies and a ragdoll pops out of no where it doent look real so thats why i want to do this. (and i know this questions been asked but that wasent really a way to do it);