Want to make checkbox checked in Bootstrap Admin LTE theme using AJAX and PHP

I want to make checkbox checked while editing any entry in Bootstrap Admin LTE theme using AJAX and PHP.

I can get and display all other fields data like this: $returnData['field']['field_name'];

But not sure how to make the checkbox checked... I tried using:

$returnData['checkbox']['checkbox_field_name'];

But it didn't work for me as I'm assuming its not the right way.

I would appreciate if someone can help on understanding the correct way of doing this.

Thanks