hello i have to drill a hole through a cube
how does it work ?

Draw a circle where you want the hole. Circle can be away from the cube. Perform Boolean Diff. The cube is the base object and the circle is the object to subtract.

You can also Boolean Diff a cylinder if you want a hole that does not go completely through the cube (blind hole). Cylinder can be made by extruding the circle to the desired depth.

http://moi3d.com/3.0/docs/tutorials.htm

Also click the Help button in lower right of the MoI screen for the User Manual.

Ed Ferguson