Dear Himangshu, if your question is how to generate the code, please login to AIIMS official website. If you not able to login, change the password by clicking 'Forgot Password'. Once you login,  Go to 'My Account' and click on 'Dashboard'. You will see a link there. Click on the link to generate the code. This code will also be sent to your registered Email and Mobile no#. Now using the link, complete the final registration process. You might face issues while generating the code or completing the financial registration process. Try clearing the cache, browsing history, restart your device and relogin.