not abt where bt abt how!!!!!!!

Big CA firm prefers both group IPCC candidates only........... and further while selecting the candidate graduation also matters. All big firms gives priority to B.comm complete candidates and now answer to your question how to apply is ...go to the website of Each firm.....there you will found apply online option ....use it and proceed further.

Another way of approaching Big size ca firm is appliying through refference of any person who is already  employed with that firm.

Best of luck

Regards

Madhusudan