Need help in connecting 2nd WIFI router along with PPPoE connection

Device and Software:
Model: Cudy WR1300 v3
Firmware Version: OpenWrt 23.05.3 r23809-234f1a2efa
Kernel Version: 5.15.150

I am a IoT hobbyist, who is new to networking. My router is connected to my ISP via PPPoE through WAN port and at the same time I want to use WAN port as switch to LAN1 for connecting a 2nd wifi router via cable from LAN1 to 2ndWAN for a 2nd PPPoE connection.

moreover, if you point me toward a video or guide on basics to setup the following, It would be much appreciated.

Thank you in advance :pray: :pray: :pray: :pray:

I'm going to try to simplify your request:

You want to add a second router and add their radios (APs) to your nework?

No, actually I have two PPPoE users for two routers but I don't have any switches to connect two routers via cable. Now I want to make LAN1 of router1 to work as switch, so that I can connect my 2nd router for 2nd PPPoE connection.

It is alread a switched port; you just need to configure it.

You can even make it wan2 but I have never done it so someone else will need to answer if you can bond the two into one.