For starters if you’re using an all in one modem from your ISP make sure that your openWRT router is connected to it.
Then make sure that either DMZ is enabled on your modem for the openWRT router.
bridged mode is enabled on your modem.
Either way works. If you don’t do this your port forwards on the openWRT router won’t work.
Actual Port Forwarding Guide
For now this will be a text only guide. I will add screenshots when I get the chance.
1. Navigate to “Firewall” then go to the “Port Forwards” Tab
2. Type in the name of the port forward. Choose the protocol you want. Type in the port you wanted forward under “External Port”. This will automatically fill out “Internal Port” as well. For internal IP address choose the local IP of the computer that you wanted the port forward to redirect to.
3. Click add
4. Then Click “Save & Apply”