Exporting a client certificate
From SNIC Documentation
In order to use your client certificate for tasks other than authenticating your browser sessions, you might need to export it to a protected file which you can then import into browsers on other machines, import into other browsers, and upload to SNIC resources where it can be used to generate proxy certificates for use with client tools.
NOTE: When possible, it is generally preferred (and easier) to obtain a new (additional) certificate in web browsers rather than transfer certificates between browsers/machines.
The export process differs between operating systems and browsers, the following links outline the process for the common browsers and operating systems, resulting in a .p12 or .pfx file.