After adding page in the footer bar widgets, each pages of my website automatically added.
But I want to add specific pages like – Amazon Disclaimer, Contact, Privacy Policy and Terms of Service.
Also I want to show this pages bottom of the footer as like this website https://flushguide.com
You need to create a Menu in Dashboard > Appearance > Menus, just save the menu with a name eg. Footer Bar. Then you can select that Menu in your Navigation Widget.
To center align the Menu go to Customizer > Layout > Footer and set the Footer Bar Alignment to Center.
Do you want the disclaimer above the Menu ?
If so remove the Disclaimer from the Copyright info and add it to a new Footer Bar Widget and place it before your Navigation widget.