Empires are built from stone and timber and fed by grain. Without resources, even the grandest ambitions crumble to dust. Claim what the land offers before your rivals do - gathering resources is the first step to greatness.
Put one (two*) action cube on a warehouse you would like to replenish with resources.
Spot all hexes with your undepleted peasants, from where you can gather the chosen 
resource. Gather from each mentioned hex 1 resource more than the number of your peasants there.
Gathering resources on different terrains:
Meadow, sea
Forest
Mountains
Hex Yield: Each hex with your undepleted peasants yields 1 more resource than the number of peasants there. For example, 2 peasants on one hex collect 3 resources, but 2 peasants on different hexes collect 4 resources in total.
Repeat: In your turn, by choosing gathering resources as your main action, you can gather different or the same resource several times, spending your action cubes each time.
Two Cubes: If there are any action cubes on a warehouse, meaning you've gathered this resource this round already, then spend 2 action cubes to gather this resource once again.
Mike puts 1 action cube on the mill and gathers 4 with his peasants on two meadows.
Next, he puts another 2 action cubes on the mill and gathers 4 again.
After that, he puts 1 action cube on the sawmill and the quarry and gathers 3 and 4 .
