To do this, you download your project and unzip / unpack it. In this example we are using Adobe Reader to view PDF's. If you don't have it click here and then click "Download Acrobat Reader". Also you can see this article to view in the Studio the way your book will look instead of doing the below way.
To view it simular to a book, in the Adobe Reader program, click "View" then "Page Display" and if "Two Page View" is not checked, then click it. Also check "Show Gaps Between Pages" and "Show Cover Page in Two Page View".
Also, click "Edit" from the menu and click "Preferences". Change the drop down "Page Layout" to Two-Up and "Zoom" to Fit Page. This will ensure everytime you open the program it will load the same. You may have to close Adobe and open back up to apply changes.
Now that is done, open your file where you Unzipped / Unpacked your interior.
When you open it in adobe, you will see only one page. That is normal, it is showing you Page 1, or cover page.
Now click on the down arrow in the menu area. Now you will see a 2 page layout like a book. Just keep clicking the down button to go through it. Up button to go back up.
After uploading you Cover and Interior (Manuscript) on KDP, you show always click "Launch Previewer" and go through page by page. If there is any issue's it will a lot of times show you them. It on;y takes a minute to do and can save you a lot of headaches by using their previewer.