Certificates can be related to a server (e.g. RDS server) or related to a certification authority.
Depending on the configuration of the network you can import only the CA certificate or both of them.
Certificates must be generated in PEM format, which can have the extensions .pem or .crt. For more information, please refer to RFC 7468, Section 5.
Certificates saved in other formats cannot be read by the device.
To install certificates on the device use the Certificate Manager available in the Control Panel.