I might be dumb but how do I root z2?

So I have ownedd a z2 for a year and a half now and still haven't rooted it. I want to do it now as I have time to do it. but how do I do it? All the tutorials I have found is outdated and im to much of a noob to find out how to do it myself.

I would really appreciate it if anyone here would be kind enough to tell me some steps on what I need to do. :)