How to join Indian Customs after Commerce degree??? What are the basic requirements to apply???

In the order to join Indian Customs after Commerce degree you need to appear in the UPSC Civil Services examination. following are the details of this examination:

Nationality:
A candidate must be a citizen of:
A citizen of India, or
A subject of Nepal, or
A subject of Bhutan, or
A Tibetan refugee who came over to India before 1st January, 1962 with the intention of permanently settling in India, or
a person of Indian origin who has migrated from Pakistan, Sri Lanka, Burma, East African countries of Kenya, Uganda, the United Republic of Tanzania, Zambia, Malawi, Zaire, Ethiopia and Vietnam with the intention of permanently settling in India.

Eligibility
The candidate must hold a degree of any of Universities incorporated by an Act of the Central or State Legislature in India with good academic record………………

Age Limits
Candidate must have attained the age of 21 years and must not have attained the age of 30 years on 1st August…………..

Numbers of Attempts
General candidates- 4 times
OBC- 7 times
SC/ST- No such restriction