WISP operator (how to access device via WAN port?)

Device wont be directly connected to the internet.
As i have a private lan.

Now i have tried everything (mostly codes to paste on firewall).
Nothing works.

Is there a complete guide for accessing the device via WAN port?
I have tried tenda, tplink etc. with stock firmware. and opening access via wan is very straight foward.


Accessing the OpenWrt. Beware though!
Port forwarding