Ration storage is limited by the capacity of your Cold Storage Depots, while Fuel and Munition storage is limited by the capacity of your Supply Depots. To increase storage capacity, you must upgrade these Buildings, as well as your Munitions Factories and Wellheads, which also have storage facilities. Fuel and Munitions in these Buildings can be moved to your main stockpiles by tapping the icons above the Refinery and Munitions Fabricator respectively.
Please note that once your Resource storage is full, any further Resources produced will go to waste.