the registration page http://acm.iitkgp.ac.in/?page=indian_reg of iit kharagpur says that step1 is following:
I . On Codechef Site
*Participants are responsible for the registration.
Every member from a team should register individually on the website http://www.codechef.com/ and create a login ID for themselves. Once registrations are over , we will provide you a team login ID which will be used by the team during the Online Prelims as well as the on-site regionals.Please note that the mock test is not a team event , every member can participate for the mocktest individually with their codechef login IDs.
To help you get acquainted with the contest we are organizing a mock test on 21st October, 2012 to be held on http://www.codechef.com/.
i am not able to find where to register on codechef to get the team id!!