Usually a tool like this:
But that is one crazy spring clip mounting. And since it going to be done from underneath (keeping all the cushion and such on) not sure if that tool will work per directions. Be careful, springs can be dangerous. Especially when you are struggling to get that last 1/8" to hook them in. Not a pro here, but I'd make a tool based on a threaded rod and wrench it over. (but I got all sorts of cool fab tools/machines)