Tax Year Prior to 2020: Hi, I need to change my income on line 5 of my 1040EZ form to $6300. How do I do this ?

Line 5 of the Form 1040EZ is not an "income" line.  It is an exemption/deduction line.  Are you trying to change from non-dependent to a dependent?

Yes I am !

My mother can claim me but I was told to fix this and put $6300 in this line, I made a mistake on this line.

You actually have to change it in the Personal Information area.  In the beginning of doing your taxes, you are asked the questions about your support and if some else can claim you as a dependent.  You have to go back to the Personal Information area to change your answers to those questions in order to change Line 5 of Form 1040EZ.