How to install intermediate certificate?

Hi folks! I’m a very noob about certificate and related, so…please, be patient. :wink:
For a couple of year I’ve put my private key and my root certificate in SSL folder of my HA server, but some days ago, sifting through the browser looking for information on the certificate I realized that is possibile to make a chain of certificate and to not expose the root certifcate.
How to do it?
My issuer send my a .ca-bundle a .crt and a .p7b? so… what the hell are all these files? what should I do with it? (obviously the one that I know, and that I used is only the .crt).
I guess that the .ca.budle is the one involved on the chain… is possible to import on HA like a normal CRT?