so my router is TP-link wR740N 150 mbps router and there is someone connected to it how i disable it or remove from network and from this whole world one and for all.
No, that is not the username. You will find the username in the manual/guide that came with the router/modem that you're connecting to. Also, the password is not the password of your wifi network, it can also be found in the manual/guide.
If there is no password to connect to the wireless network, create one.
Also, you may be able to ban the MAC address of the computer that's connected (page 41 - http://www.tp-link.com/resources/document/TL-WR740N_V4_User_Guide_1910010596.pdf).
yes i tried with ip automatically obtained it just repeats the box with user name and password admin and with manually assaigned ip it shows blank page.
No, that is not the username. You will find the username in the manual/guide that came with the router/modem that you're connecting to. Also, the password is not the password of your wifi network, it can also be found in the manual/guide.