There is no prescribe syllabus for BHUPET so it is advisable to go through what you have studied in your graduation and once you are done with it, you can start doing previous year papers as these will be helpful to know all the important questions, difficulty level of questions and the paper pattern so you are advised to do the same and you are good to go.

You can also download old question papers from below link -

http://bhuonline.in/old-qus-paper-entr.html

Good Luck!!!