You should read through this entire document before installing the certificate. The link to our certificate is at the bottom of the page.
These instructions were built on a machine running Windows 2000 with Opera 6.01 installed. The procedure on your machine may differ slightly.
1) Click on the certificate link at the bottom of this page.

2) Ensure that the checkbox beside "Allow connections to sites certified by this authority" is checked. Then click the "OK" button in the window above. You're done!