Hello Anumula,

For preparing for BITSAT you really don't have to study differently. The level of examination is almost the same as JEE advance and bit higher than JEE Mains. So you have to put in the same amount of hard work as you're putting in for JEE Advance. 

Along with that you have to prepare for English and Logical Reasoning. For preparing these subjects time and attention amount of hard work you have to put in depends upon person to person, As some have good command over theses subjects and some have a little less. I would suggest you to take the previous year papers of BITSAT that will help you to understand the exam.

Hope this will help you.