The Institute pin code in CTET form is the pin code of the college the applicant pursued graduate or post graduate studies from. This detail is filled in addition to %age, state, name of degree under the education section.

For more information, you can refer to the link below:

https://ctet.nic.in/CMS/Handler/FileHandler.ashx?i=File&ii=147&iii=Y

Hope this helps. Good luck.