Hello,

In 12th or equivalent examination details select the passing status clicking on the drop down box. As you have already passed Diploma select 'passed' in the qualifying examination. Next select the year of passing in the qualifying examination. Next in qualifying examination details click on the drop down menu the list of equivalent examinations will be displayed select  'A Diploma recognized by AICTE or a state board of Technical Education of at least 3 year duration.....' fill all the details, enter security pin, save the details and proceed to fill additional details, upload the documents and submit the application.

You can refer JEE Main 2022 Information Brochure while filling JEE Main application which is available on the official website

https://jeemain.nta.nic.in/