How to get 4K & 120fps video feature with L camara in nexus 5 topic

I have recently rooted my nexus 5(5.0.1). I want to get 4K and 60/120fps video capturing feature with L camara on my phone. I also have installed L camara and also tried to install this feature but I couldnt. So give me step by step method for installing this feature. Waiting for reply... Thanxx