also
System/Startup/Firewall (disable)
Network/Interfaces/LAN (disable DHCP and all DHCPv6 services)
(assign IP address i.e. 192.168.1.253)
(assign gateway i.e. 192.168.1.1)
(assign DNS i.e. 192.168.1.1)
P.S. your TL-WR841N is old, substitute WAN for LAN1 in the pic, max vlan IDs up to 15, your wan port on eth0 or eth1 so may not be usable for a managed switch, my example show the WAN port on vlan2 or eth0.2