BITSAT is not so different from old AIEEE exam or new JEE format. So you don’t need to do special preparation for that. The question pattern is very similar to AIEEE or JEE. Only the medium of exam is computer based, which I guess some regional boards have adopted nowadays. So don’t bother yourselves too much wih the details.
BITSAT has an additional session wih English and Aptitude, which is very similar to a general IQ test or aptitude test.
So I have listed out the outline of BITSAT exam. Now a little bit on how to prepare for it.
First thing, make your basics strong. Learn them such that you cannot forget it ever. This is the first and foremost thing you need to focus on for any entrance exam. Then a few weeks before BITSAT, practice the BITSAT style computer based exams. You will get good resources online and through arihant book series.
Now, get out of Quora and start working your ass off.