Add more LAN Ports

I apologize, but step 2.2 above:  “Use the WAN port on the cambiar, and use any of the Ethernet ports on the gateway" has me confused for a couple of reasons.  Is it supposed to be the WAN port on the  gateway, and the ethernet ports on the cambiar?  Or if it is correct as written, how can you tell the WAN port on the switch when they are merely labeled 1-8 (but there is a small notation of “Link/Act” above port #8 on the TP-Link TL-SG108).

Secondly, if this is backward and I am looking for the WAN port on the gateway, then I still am confused, as I have the newer flat white 5G gateway, and all there are on it are two yellow LANs and a USB-C.  Would this setup still work just plugging into one of the LANs on the gateway?

¡Gracias!