Pls help me..how to do internal audit?

This may help.

https://icai.org/new_post.html?post_id=597&c_id=145

Analyse the operation company carry out and the kind of jobs(manufacturing/service) the company undertakes.

Analyse the accounts records maintained by company, its system of accounting, accounting policies, standard operating practices, etc. Understanding the business of the client (indepth) will help you understand the key areas and in the course of understanding only you will come to know about the "risk areas" in the audit.

Get the Standard operating procedures of the management. An SOP is the procedure which the company normally follows to carry out its day to day business operation. This will give you a clear guideline how the organisation functions. Get several manuals (like HR manual), see company's policy and see its compliance by performing walkthroughs and indepth checking.

You will be able to draft an audit programe, review it and finalise the audit programe... its a continuous process. you can modify the audit programme as and when the audit progresses.

Generally the management prepares an audit programme and identifies the areas to be covered. You can talk to the top management/appointing authority and ask them identify the key areas.