Change size of the image on entity form

I have a client form which has the image of a client on the top left corner. Currently, whatever image I upload, it is getting reduced to 144x144. I want to change the size of that box to 400x400 to display the image. Attaching the screenshot below.

I'm new to dynamics, so don't know how to approach this problem.  Please, suggest all the possible ways I can use to achieve the end result.

Any help is appreciated.
Thanks