Interfaces to Xconq have two major modes governing how input will be handled; survey mode and move mode. The purpose of these modes is to streamline the input and interaction process; they have no other consequence, and all functionality should be available in either mode.
In survey mode, you are basically just looking around the map. Normal left-button mouse clicks change the focus and perhaps scroll the map, but do not cause any units to do anything.
In move mode, a normal left-button click means to move the currently selected unit (or units, if on Mac) to the location clicked upon.
In both modes, right-click will move the selected unit(s).