The only way you can change the amount on Line 1 of Form IT-201 is to go back to your federal return.  Income from wages, salaries and tips on the federal return gets transferred to the state return (line 1). You will see the income listed on the following lines of the federal return, depending on what federal form you filed.

Form 1040-line 7

Form 1040A-line 7

Form 1040EZ-line 1