1st you must check if your modem/router is broadcasting wireless network .
to know that , log in to his page and check wireless configuration .
goto your browser and put this ip : 192.168.1.1
username : admin
password : admin
then goto Wireless connection on menu
Configure it with an ssd name you want ex: my wi-fi
configure password as wpa2-psk your password
enable broadcast
after that , save configuration on router and goto your laptop
disconnect your lan cable
seach for wireless networks
You should find your network ex: "my wi-fi" there
click on it and put the password you used in wireless configuration on router .
after that you shall connect to net .
you should red your manual of router for any doubts .
get it here :
ftp://support.dlink.co.in/broadband/DSL-2730U/manual/DSL-2730U_Manual_v1.00%28WW%29.pdf