The other day i helped my friend configure a TPLINK wireless router with an ADSL modem, from my experience, there are two possibilities: one is bridged ADSL &TL- WR740N, if this is your case, configure tplink router's WAN as PPPOE (if your ISP uses PPPOE); the other is ADSL with PPPOE settings &TL- WR740N, in this case, you need to configure dynamic IP for the router's WAN. Perhaps, you can find some nice instructions on TPLINK website.

Thanks for replying. Actually i have tried your way. But, it did'nt worked out. And i use ADSL router not ADSL modem.

okay.. you use ADSL router. That also should be OK when you configure dynamic IP for the TL-WR740N's WAN.
The IP address of your ADSL router and TL-WR740N must be different. And they are in different IP range. For example, if your ADSL uses 192.168.1.1, change the WR740 to 192.168.2.1.

SAME PROB
dlink adsl 2 - 2750u router + modem
cant brigde

The Dlink ADSL2+ Modem assigns dynamic ip in DHCP Mode ... ( I have assumed that your D Link modem dials automatically)

OK.. Do this

You need a LAN Cable
Connect the lan cable One end to your PC and other end to LAN PORT of TP Link router

Open Internet Browser and type 192.168.1.1 hit enter Login : admin Password : admin

Now

Network > LAN > IP Adress : 192.168.1.1 (change it to 192.168.1.112)
Network > WAN > Wan Type > Static IP > Ip adress : 192.168.1.113 , Subnet : 255.255.255.0 , Default Gateway : 192.168.1.1 , Primary DNS : 8.8.8.8 , Secondary DNS : 8.8.4.4

*** SAVE AND REBOOT ROUTER ***

Now reopen Internet Browser > 192.168.1.112 hit enter Username : admin Password :admin

DHCP > DHCP Settings > Enable it > Start IP : 192.168.1.150 , End IP : 192.168.1.199 , Default Gateway : 192.168.1.1 , Primary DNS : 8.8.8.8 , Secondary DNS : 8.8.4.4

**** SAVE AND REBOOT ***
Configure your Wireless Network as you want and have fun !

Now unplug lan wires from PC and LAn port of TP Link Router and plug it in WAN Port of TP Link router and the other end at your D Link modem