You would immediately receive a confirmation mail in your Personal ID along with further instructions.
As per instructions Send a D/D of amount specified in mail in favour of INDIAN TESTING BOARD, payable at 'NOIDA' to our Noida or Bangalore Office, you can find the address at http://istqb.in/contact.htm
You will be informed of the timing and procedure of the examination. Appear for the examination on the designated date, time and venue.
Please do not forget to bring a photo identity (Passport, Driving License, Election Card etc.) with you when you appear for the examination.
You will be informed of your result within two weeks and passing candidates will receive the certificate within eight weeks.