If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).
You command the red units. Kill the green units. Select units by clicking on them, move them by clicking on the ground and attack enemies by clicking on them. You can attack enemies with crosshairs on them especially the ones that come in contact. Watch out for the number of units in the squad, you don't wanna be left alone. You can also buy vehicles and guns. Advance your line to the enemy's line to win the mission. Are you ready to give commands?