Need help with adjusting book cover size on Amazon self publish

I am close to publishing my paperback book.I want it to be a 4.5inch by 4.5inch. im struggling to get it to that size and to fix the cover right on the front
https://kdp.amazon.com/print-preview?token=eyJpZCI6IjRkNDQzZDA2LWY3ZTItNDViNi05ODE3LWE0ZWMxNzg1YjJjNyIsImV4cGlyYXRpb24iOjE1Mzk2MTE4MjYxMzl9%7CeyJtYXRlcmlhbFNlcmlhbCI6MSwiaG1hYyI6IkJpR3ZFTGgvb2ZvTmtzb0dwQTgyVWNqenJEb0xpcmRkaTdzcEMvSSt6M2c9In0&transform=original&certifiedDate=&locale=en_US&redirect=%2Ftitle-setup%2Fpaperback%2FPMA4TYHB61S%2Fcontent