u need to use it as a router, not as a access point
u need to assign it a diff network IP, eg if ur modem is 192.168.1.1, set router to 192.168.2.1
enable DHCP on modem and TpLink
enable Wifi and Wifi WPA security on TpLink
plug modem LAN out into TpLink internet LAN IN port
u should be done.