Found this post may be able to help you.
My home, i'm using 2 routers (DIR 868L)
Router 1 in the living room, router 2 in my bedroom
Router 1 as per normal, connects to the ONT, and router 2, connects form LAN 1 of Router 1 to "Internet" port of Router 2.
Go to Settings DLINK, http://192.168.0.1, then go to Manually configureset router IP address to 192.168.1.1
Enable DHCP servcer on the router, change the client IP address to 192.168.1.100 - 192.168.1.199 (Range)
I usually not fussy about usernames, and just use default. Easier to set that way when i reset in future. But for added security, remember to set your own SSID and password