Hello mate
The same happened to mine and it's dead easy to fit. Basically if you want to take the old one off first then pull it up so that it looks inside out and you shoulod see a cable tie that keeps the top fastened to the gear lever. Just cut that off and you'll see there's a ring that goes round where you need to fit the new one.
Then take the new one, attach the top end using the new cable tie, which you should get with the cover, and then slide it down and clip in the bottom. Make sure you are happy with how it sits before you clip in the bottom though cos otherwise you'll have to snap it and start again. Hope this helps.
Jono