To be able to use the certs for open vpn or openswan, you need to export them in the correct format. This is normally PEM. Now choose the certificate you want to export and press Export. You will get a window asking for some options:

After you exported all required certs, change to the key view of the main window.

Choose the key, press Export and you will get a similar window as before. With one difference, you will be asked if you want to export the key with or without a passphrase. Choose no, so you will export it with a passphrase securing the private key.

After exporting all your keys, go to the CA view of the main window and choose Export Ca which will get you another export window. Choose PEM Format, too.

The Last thing to export is the CRL (Certificate revocation list), to do this, choose Export CRL from the CA view. You might set the value of how long this list is valid to a value greater than 30 days. If this matters at all changes with the software you want to use this cert with. You can , for example, configure openswan to reject connections when the crl is not up to date. Choosing a value of 90 days means that you have to export a new crl in the next 90 days regardless whether you revoke a cert or not...