What we should consider while audit in a company

hello,

my self vishal jain, ca-ipcc student doing articleship in ca firm

and i am on internal audit in a company

because of new articleship joining by me , i dnt have much experiance about how & what to check purchase, sales regiser, journal

cash ,bank etc.
so, i request you to plz, suggest me how i m becoming an efficient auditor & article as well