Hii!
There are two ways you can access in the previous year question papers. First, you can purchase the books from a book store or second, you can search online for them. The link given below will help you download the previous year question papers of various subjects, such as maths, physics, biology etc.,

https://www.google.com/amp/s/school.careers360.com/articles/odisha-chse-questions-paper/amp

Hope this helps.
Good luck!