edit array in ember.js inside javascript file

I have declared an array in ember as shown below.

checkboxList:[{VALUE: "Content", CHECKBOX_ID: 1},{VALUE: "Size", CHECKBOX_ID: 2}],

I want to change the value in the first object from 'Content' to 'Contents' in another part of the program.

I tried to do the following :

this.set('checkboxList.[0].VALUE', "Cont");

But it did not work. Could anyone help me out with this ?

Thanks in advance :)