Mining is a great way to gather resources to upgrade your Base and expand your Army. Various Resource nodes are scattered all around the Map for you to mine. To mine resources all you need to do is to send a Squad of Units to an unoccupied Resource node, Supply Drop, Farm, Fuel Depot, on the Map. The Squad will start gathering resources once they arrive and they will automatically return to your Base with the Resources when their cargo space is full or if the node gets depleted. You can also manually withdraw your mining Squad by tapping it and choosing to Call back.
Resource nodes do not replenish over time, but new ones will spawn randomly around the Map.