Open System Preferences > Network from Mac applications menu.
Click the "+" button to create a new service, then select VPN as the interface type, and choose L2TP over IPsec from the pull-down menu.
Server Address: Enter
Account Name: Enter Windows Domain Username
Click Authentication Settings and provide the following information:
User Authentication > Password: Enter Windows Domain Password
Machine Authentication > Shared Secret: ENTER SECRET
Click OK to go back to the main VPN settings page
Click Advanced and enable the Send all traffic over VPN connection option.