OpenSCAD User Manual/First Steps/Opening an existing example model

Open one of the many examples that come with OpenSCAD (File, Examples). Or you can copy and paste this simple example into the OpenSCAD window:

Usage example 1

difference() {
    cube(30, center=true);
    sphere(20);
}
translate([0, 0, 30]) {
    cylinder(h=40, r=10);
}

Then press F5 to get a graphical preview of what you typed (or press F6 to get a graphical view).

You get three types of movement in the preview frame:

Drag with left mouse button to rotate the view around the rotation center (view with ctrl-3) along the X and Z Axis. The bottom line changes the rotate values. (use shift while left-drag to rotate around X and Y )
Drag with any other mouse button (or control-drag under OSX) to translate (move) the view. The bottom line changes translate values.
Use the mouse scroll to zoom in and out. Alternatively you can use the + and - keys, or right-drag with the mouse while pressing a shift key (or control-shift-drag under OSX). The Viewport line at the bottom of the window shows a change in the distance value.

See also edit