[Select multiple units]
Hold the Left Mouse Button and mark the mouse to drag a selection box over the units.

[To issue an attack order]
Select the unit or units and Right Click on a valid target.

[To capture a unit]
Left Click the "Capture" icon in the Special Abilities menu and Left Click again on the unit you want to capture.

[To select all of a specific type of unit]
Double-Click the Left Mouse button on one of that type of unit.

[To build a structure]
Select your ACU or an Engineer. Click the icon of the structure you want to build from the Build Menu. Place it on valid terrain to begin construction.

[To build a Rock Head Tank]
Select a Land Factory. Click on the Rock Head Tank icon to build one unit. Click it multiple times to queue up multiple units.

[To set a Rally Points for a factory]
Select the factory and Right Click on a valid destination. The next unit build will automatically move to that location.

[To build an Add-On]
Select a Land Factory. Select the Add-On Tab. Click on the icon for the Add-On you want to build.