Click to select and place barracks/towers to train new units. You can only place your buildings on level ground. When you select a building, a flag will appear. Move it, by holding the Shift key while you click, to the spot where you want your troops to rally. At the bottom of the screen, you will see the units you can train. Click an icon to train a new unit (watching your budget). Click and drag to select soldiers, and then click where you want them to attack. Between locations, assign the skill points you've earned to improve your battle skills.