I understand that you needed to access your ebooks purchased from Amazon through your Samsung Tablet 4. Since you have purchased it from Amazon and able to read it through iMac, you may access it from your android tablet S4 by installing Kindle app from android store. Once installed it n your tablet, you may sign into it using your amazon account and then you can access all your ebooks purchased from Amazon.
You may download the Kindle app from Google play store
Thank you. Have a great day!!!