As much I know the slot booking is to begin from the 3rd week of march. The online registration ends on 21st march soon after that may be or some days before it the booking might start. I suggest you should keep a track now. As the slots are quite few and students appearing the exams quite a lot so the slots will get filled up very quickly. To get a slot of your interest you should do it quickly. 

Dont wait for too long. I hope this helps.

Hello Jaspreet,

The Slot booking link for VITEEE conducted by Vellore Institute of Technology will be available in its website by the 4th week of march tentatively as per official information available currently.

Hope this answers your query, feel free to ask for more info.