Is there a proper way to put in pushrods for a Volkswagen engine 1600cc?

Well...kind of. There's a recess in the cam follower (which is way inside your engine) that accepts one end of the pushrod and a recess in the rocker that accepts the other end. Pushrods are the same at both ends. So... Start by rolling the pushrod on a flat surface. If it won't roll, it's bent and you need a new one. Stick the pushrods into their holes, then install and torque the rocker arm. Adjust your valves, install the valve cover and you're done.