connection to a network with security certificate

Hy, I’m new of linux, I want to connect to my School network. I requested a security certificate. They gave me a .p12 file. I don’t know how to access to take my security code. I use Open Suse 11.0. When I try to open the file with kleopatra it says that there is an error. What can I do? Please try to explain me easily because I’m not very skilled.
Thank you.