Which particular course you want to go for and to get admission in UG programs like BA,B.Com, B.Sc in BHU you will have to crack BHU UET and there is no prescribed BHU UET 2018 syllabus so your 11th-12th syllabus would be there.

Apart from that, you can practice sample papers and previous question papers as this would be enough.

Below I am providing sample papers and question papers which you can download -

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

https://university.careers360.com/download/sample-papers

Also, if you want to go for B.Tech then you will have to crack Jee advanced as to be eligible for IIT BHU you should have secured 75% marks in your boards or you should be there in top 20 percentile and for SC/ST you should have 65% marks.

To know more about Jee advanced 2018, you can go through below link-

https://engineering.careers360.com/articles/jee-advanced

Good Luck!!!