Private to public IP address for use with Asus VPN InstaGuard

I have gig fiber to an ONT to a TP Link Er605 router in my coms box outside. I have an ASUS AIMESH system behind that which says my IP address is private because it’s behind the TP Link. I want to be able to use Asus VPN InstaGuard but I’m not able to because the IP is private. I read on the Asus website that I can fix this problem by port forwarding. I have tried to port forward on the TP link and the Asus router and can’t seem to figure this out.

Question by Brian vanMastrigt on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.