Select: left-click a unit, or drag a box around many. Double-click selects all of that kind on screen.
Orders: right-click the ground to walk, a tree, gold, stone, berries or sheep to gather, an enemy to attack.
Build: select villagers, pick a building at the bottom right, then click the ground. Right-click cancels.
Train: click a building, then a unit button. Right-click the ground to set where new units go.
Camera: slide two fingers on the trackpad to move the map, pinch to zoom. Arrow keys, the screen edge, a mouse wheel and + / − work too. Click the little map to jump. Turn the view with the two arrow buttons at the top, the [ and ] keys, or a two-finger twist.
Walls: select villagers, press Walls, pick a fence or wall, then click where it starts and click (or drag) to where it ends. Gates let your own people through.
Win: grow your people, reach the Feudal Age for your special unit, and defeat your rival: destroy their Town Center, their villagers and their army before they destroy yours.
Keys: H = town center, . = idle villager, Space = go to selection, Esc = cancel, P = pause. The letters shown on buttons work too.