Thanks. Tried it once just now and it didn't work. this method requires me to put the main router and the access point next to each other right? (since I need to use a cable to connect both devices), but what if I want to put the access point in my room where is the signal is weak and the main router is in the living room.

The router that I am going to use as an extender or access point is not a TP-Link N router.
Just wonder if all routers can be used as an extender or access point.

Actually, TP-LINK AC1350 Wireless Dual Band Router Archer C60 (5 antenna) used to be my main router and I used another TP-Link (old model with 2 antenna) as an extender. However, I went to Unifi  to change my plan land they gave me a D-link router (four antenna) as my main router. So I am now thinking of using  TP-LINK AC1350 Wireless Dual Band Router Archer C60 as my extender now.
Thanks.