Right now you can not be apply for Login process because last date for Gate 2013 has passed so you can apply next year in Sept month.

For login you should register your self on Gate 2014 and you should enter following details
Name:-
Email:-
Password
after that you are able for apply online and again when fill up application for payment or reprint the you can use your Email Address and password

Here i am giving you screen shot for Gate Login IIT