If you are asking about how to apply for admission to Diploma in Engineering at JMI, the dates for 2018 have not yet been updated on their website. In the meantime go through the prospectus of 2017-2018 admissions to get a fair idea of the eligibility, likely dates and admission process from the below link

http://jmicoe.in.s3.amazonaws.com/pdf17/JMI-prospectus-2017-18.pdf

Keep checking JMI website for admission 2018 notfication: http://jmicoe.in