How to prepare income statement

It all depends on what stuff you've got involved, what kind of company it is, and what level you are at. The gist of an income statement is revenues and expenses, the difference of which makes net income. But it's always difficult when people ask this so vaguely when we don't know how far along you are or what is involved.

Here are just some examples:
Principles of Accounting Chapter 4 (http://www.principlesofaccounting.com/chapter%204.htm#PREPARING%20FINANCIAL%20STATEMENTS )
(Scroll down a bit.)
Principles of Accounting Chapter 5 (http://www.principlesofaccounting.com/chapter%205.htm#Income%20Statement%20Enhancements)
Single-Step Income Statement | AccountingCoach.com (http://www.accountingcoach.com/online-accounting-course/04Xpg03.html#income-statement-single-step)
Multiple-Step Income Statement | AccountingCoach.com (http://www.accountingcoach.com/online-accounting-course/04Xpg04.html#income-statement-multiple-step)

There should be examples in your book, which will give you a much better idea of what you are expected to be doing at whatever level/topic area you are at.