Hi,
With your browser, point to the address of the certificate and save the file on your disk. Double click on the file and the Certificate Installation wizard will start. Because the certificate is self signed, Internet explorer will automatically install it in the Trusted root Certificate Authority list. From now on, Internet Explorer won't complain and any Certificate signed with this root CA Certificate will be trusted too.
You can also open it from Internet explorer which will display the certificate. Click on the button Install Certificate to launch the Certificate Installation wizard.
Rgds.