Installing SSL

I am attempting to try and install a comodo ssl certificate to my domain. Howeverit keeps saying

Certificate does not match

or

DNS Redirection problem for rosalinebettencourt.com with www and without it

. What am I doing wrong, am I not copying the correct certificate?

I tried placing all three into the "certificate authority" section.

https://imgur.com/a/Uc0Q5qK

You need the private key you used to generate the CSR.  You also need the certificate that they issued, along with the CA bundle they issued.  If all 3 don't make a chain, you will get that error.