See the pictures in this guide, they will help. Look at the very first steps, you need to take out first your back cover and then the white plastic middle plate into which the camera lens is glued to. Then maybe use some heat (a microwave heat pouch or a hairdryer on low heat maybe? Be cautious and don’t apply too much heat…) to soften the glue and remove the piece of broken glass with a knife. After that you’ll be good to go to apply the replacement piece! If it’s your first time with repairing anything like this then it might take some experiment - but otherwise this should be an easy repair. Good luck, let me know how it turns out!