Hey Naveen.

Yes, you can write the April session of JEE Mains if you've attempted the January session. You need to register for the same. The April session of JEE Mains is scheduled to be conducted on 6th April, 2019.

For the JEE Mains April Session the Application Form will be released on  February 8, 2019. The applications can be filled till    March 7, 2019 for the April session.

In order to compute the final ranks of the best of the two marks from both sessions will be considered. Hence the session in which you score higher marks will be considered for computing the ranks.

You can use the link below for applying as soon as the form is released and for other details and updates as well.

Https://www.google.com/amp/s/engineering.careers360.com/articles/jee-main-april/amp

Best of luck