While Command Hud option (press hold Left Shift button) is accessible during realtime gameplay. This option allows you to momentarily pause the game, thus giving you enough time to, give orders to your squad or perform some special moves(move to location, attack or make use of some special powers ..etc)
You may have noticed that while in command the cross-hair is locked in the middle of the screen, thus limiting a lot of options.
To move it simply click and hold the right mouse, this will give you the opportunity to pinpoint all your attacks on a single or multiple enemies.
Simply release the Shift key and all the predefined actions shall be performed.