Prefab initializing on runtime is not possible on Unity 5.3.0f

I just updated my Unity Editor to 5.3.0f3(2017) and previously i used to assign my prefabs onto a GameObject at runtime however now I am not able to do it because there is no dialouguebox appearing to drag and drop the prefab.Can anybody tell me a proper way for initializing a prefab onto a game object because i tried some code but didn’t work out or a better way to do this?3364620--263647--bandicam 2018-01-23 16-46-02-149.jpg

Use the [SerializeField] attribute if you want to expose a private field to Unity’s Inspector.