Local certificates

Systemwide certificates
To add a certificate (for example your or your organization's internal CA certificate) to the systemwide list of trusted certificates, place the new certificate in. Be sure, that certificate name ends with .crt (and not with .pem).

Make sure users have necessary read access to the directory/certificates, or users won't trust them due to read failures. Also make sure untrusted users don't have write access!

Then either run or rebuild  with  to add the certificates to.

Chromium
Chromium (like many other web browsers) do not use the systemwide CA certificate list.

You need to open then choose Authorities tab and import your CA certificate.