IP management throug Airport Extreme
The Airport Extreme (or Express or Time Capsule) don't have any VPN functionalities. I mean, apart from opening a port to let you access a VPN in your home network.

So, you will need some sort of server inside your home network. Mac OS has a VPN server but it doesn't have the most friendly interface (if it has an interface at all). Once upon a time I used iVPN (http://macserve.org.uk) to help me configure it. Otherwise, Apple Server also has a graphical interface. Todd Olthoff has a great series of videos on how to set up your VPN (and Apple Server): https://www.youtube.com/watch?v=GjrcmsMHwPI