Hello Ratan,
If you wish to take admission into BHU from the sports quota, then you will have to fill the form mentioning that you want to seek that quota. Further there are few more steps that you need to follow , for more information you need to visit their official website for any updates.
Below I am leaving a link regarding their notice for the admission in BHU under the sports quota category. Refer the same for more information.

http://bhuonline.in/pdfs18/Notice-for-the-admission-under-sport-quota.pdf

Hope this helps,
Good Luck!