How to add SSL into my domain

I’ve just bought ssl certificate and they gave me zip file including 5 files but in my panel I have textarea to input Cert and Key

What should I do?

Are you using any control panel to host your domain?

Just copy and paste the crt and ca-crt into the left pane and the private key into the right, then save. Refresh the page and it will tell you if it is ok.