Click and hold your mouse over your building to select it. While still holding, move your mouse over a building you like to attack and release. To select multiple buildings, click, hold and drag across up to 15 buildings and release on a building you like to attack. Crystals on map give more crystal energy that allow you to use spells and increase speed of your troops, but they dont generate people. The more people inside, the more crystals you get. Towers are defense structures, they increase defense and attack of your troops, but they dont generate people. The more people inside, the faster it shoots. You can use spells.