Double-click on a *.p12 file. This will automatically open the Mac OS X's Keychain program, and ask you if you want to add the certificate from the file to your Keychain:
Choose your login keychain (it will either be named login, or your Mac OS X username) as the keychain to add it to, then click OK. Now you will see a list of stuff in that keychain, and you should see the new certificate in there:
...along with a possibly cryptically-named private key that goes with that certificate:
You're done! Now, you have to make sure that it's the only certificate (of your own) in your keychain, because Mac OS X won't ask you which one you want to use when authenticating to something. Here's one way you can do that:
If there's not already a keychain drawer shown to the right of the Keychain window, click the "Show Keychains" button at the upper right of the window. (If it's already shown, that button will say "Hide Keychains" instead. If you don't know what a "drawer" is, click this button anyhow and the window will change.)
Create a new keychain: choose New Keychain... from the File menu. You'll see the following window:
Name it something like "Temporary Keychain" and choose where to save it: on your Desktop works.
It'll ask you for a password to protect this keychain: choose something strong. You'll be putting your private keys in here.
Now, drag your previous certificate, along with the matching private key, into the new keychain. Repeat for any other certificates you already have. Note that you only need to erase you own certificates (those with matching private keys), not other people's.
Now, choose that keychain in the right-hand Keychains drawer, and choose Delete Keychain from the File menu. You'll see the following question:
You want to keep the file so you can reinstall those certificates and private keys later, so choose Delete References.
Later, when you want to restore those certificates, double-click on the keychain file you created, and drag everything from it back into your login keychain. Then delete the temporary keychain, and this time really delete references and files.
First, make sure you only have one certificate in your Keychain (see above).
Now, go to the wireless icon on the right side of your menubar and choose Open Internet Connect... You'll see a window something like this:
If you see an "802.1x" icon in this window, click on it. If not, go to the File menu and choose New 802.1x Connection... The window will change to this:
From the Configuration pop-up menu in this window, choose Edit Configurations.... Now you'll get this dialog box:
In the field for "Wireless Network" enter the "Authorized_User" SSID. Your username and password can be basically anything since your certificate is used instead. Click OK. Now you're back to the old Internet Connect window. Make sure your Airport card is already on, then click Connect.
If this is your first time connecting, you'll be asked to accept the Greenpass RADIUS Server's certificate. You should accept it. You'll also be asked if "eapolclient" can use your private key; let it use it.
If everything goes well, you'll see this status message at the bottom left of the Internet Connect window:
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