S33 is just a cable modem its a plug and play device so you can connect the mesh system to the modem LAN port and then setup the mesh system according to the setup guide provided for Eero router. According to the speed plan you can use the ethernet port on the modem if your speed plan is below 1Gig use the 1G LAN port or mode than 1G then you need to connect the router to the 2.5G ethernet port on the modem.