Yes, under the scenario you describe you’d plug the ethernet cable fom the main router into one of the TP-Link’s LAN ports (not its WAN/Internet port), and then in the TP Link's settings configure it as an “access point” (AP) and also disable its DHCP server setting.
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https://www.amazon.co.uk/TP-Link-Gigabit-Controller-Software-EAP225/dp/B01LRQW0GM
https://www.tp-link.com/us/support/faq/1199/
Your main router should handle all DHCP (IP address assignment) duties for the entire network.
Having two active DHCP servers on the same network can cause conflicts.