Need Help with SSL Installation on NGINX.conf settings?

I'm a new user to any sort of self managed server (VPS). I'm use to using cPanel so this is a huge learning curve for me :) which is good!
I'm running a Wordpress Site that is running on NGINX.

I've obtained an SSL Certificate via crazydomains.com.au and have received all files from them;

AddTrustExternalCARoot.crt
USERTrustRSAAddTrustCA.crt
USERTrustRSADomainValidationSecureServerCA.crt
zasel_com_au.crt

First thing I did was update the http.conf file to direct all http to https.

What I need to do is now Install the SSL Cert on my server for it to be shown.

How do I do this?
I have no idea where to begin and as it's my first time, would highly appreciate if someone can help me out.

Many Thanks