Hii Anbu!

In order to join CBI you need to go for SSC CGL entrance examination. As per the eligibility criteria, the age limit of the candidate must be in between 20-30 years of age, for general category, 20-33 years of age for OBC and 20-35 years of age for ST/SC categories.

You haven't mentioned the category you belong to. But, if you come under reserved categories, you can apply for the exam in future. If not, you can't apply now, as the forms are already been filled. Till next year recruitment, you must have completed the age limit to join.

Hope you understand.

Good luck!