Connect through VPN

i installed server 2003 and i added a DC and AD role. now i want to VPN. i added the role and obviously can VPN inside my LAN through a user account i created but i cant VPN from the outside. ive read on VPN filters however im either doing it wrong or im not getting it. can someone assist on how to set it up to access VPN out side. im currently running through a Linksys WRT150-N wireless router ive gone through the settings as far as NAT but im not using it.