If you have ''''El Capitan'''' then the built in VPN connection settings should just word. You will still need to install the Certificate as above, but you can skip the StrongSwan parts below and just use the Network Settings to add a VPN IKEv2 connection.
==Create the Connection==
#Go to Apple Menu - System Preferences
#Go to Network
#*VPN Type: IKEv2
#*Service Name: eg 'FireBrick' or 'Office'
#On the next window fill in the information
=OSX version 10.10,'Yosemite' and below=