Whenever your application needs to communicate securely to another url you'll have to import the certificate for the remote url into your environment's trust store. Sometimes a single certificate is acceptable, other times you will have to import the entire certificate chain. This will always include the Root certificate from a certificate authority and usually at least 1 intermediate certificate. all these certificates together create a chain of trust so your application can confidently trust that the remote url is who it identifies itself as.
Take for instance the attached photo of bank of america's certificate chain. The Root would be VeriSign, The intermediate would be Symantc Class 3 EV SSL CA - G3 and finally the cert you're trusting is
www.bankofamerica.com.