Depends on the version of Android and possibly the manufacturer, but in general, to add apps or widgets, open the app drawer (the place with all the apps, usually there's a circlular icon with 6 dots inside fixed in the bottom center of the screen), find the app or widget you require, press and hold until your home screens appear then drop the icon in the location you require.
To move apps or widgets on home screens, press and hold until the screen changes then move to the location you require.
To remove apps or widgets, press and hold the icon on the home page until the screen changes then drag to the x Remove bar at the top of the screen.
