Hello 

It would be suggested that check your emails and sms box, as it should be somewhere when you registered yourself. Their may be somwhere in your first mail from KCET.

If you are still not able to find the user Id, you should get in touch with KCET officials.

Regards.

Hello aspirant, 

Usually all entrance examination authorities messages the candidate user id to their registered email id and registered phone number. Check your mail and your phone for sms from KCET.If you don't get such sms, contact the kcet authority for help. 

Good luck