How to Setup Port forwarding on an Asus RT-88u Router for Windows Server 2012 r2

Anyone know how to setup port forwarding on an Asus RT-88u router for Windows Server 2012 r2 Anywher Access...I've been in I.T. for a while and I've everything I can think of...says router isn't forwarding though I have port forwarding on; I've also imported .PXE certificate ( had to convert PEM file). I just need ideas @ thispoint...my ISP provider is Comcast (probably a minus right there) and domain provider GoDaddy. Thx in advance.