This will be a generic guide for configuring your WIFI Router / Firewall as it is impossible to do screen capture for hundreds of different Router / Firewall model. The basic requirement are same and 90% of the Router / Firewall have this features called port forwarding and reserving an IP address based on MAC address. As an example I have picketed up a cheap commonly used brand called TP-Link.
Step 1
Login to your router by typing the router management IP into the web browser and hit enter. For Tenda it is 192.168.0.1
Once the login page comes up type login ID and Password.
Note: The default password is shown on the bottom of the router. If you have changed it and you also forgot it, you need to reset the router to it's factory default by pressing the reset button.
Step 2
Then the interface will turn into the homepage, tap “Advanced”, you can see “Port Forwarding” option in this page.
Step 3
Before you do the port forwarding, you may need to reserve the IP address of your node (Pi Zero 2W)
To reserve the IP address you need to know the MAC address of your node.