The Wood Storage is a new building found in the new castle update. It costs 2 Wood to place down, and takes up lots of land. When the Wood Storage is built, there is one log in it. You can collect that wood by left-clicking on the Wood Storage. To put wood into the Wood Storage, right-click on it. Others can access wood in the storage, so protect it!
Wood storages are designed to be used to store large amounts of wood for multiple groups of minions. To store wood in it, right click it. To take wood out, left click it.
Wood storages will eventually disappear when left for too long with no wood in them. They are not destroyable, so this is the only way for them to be removed from the map.
Wood storages can be used by tribes of a different faction than the one that created it.
Also keep in mind that enemy tribes can use these, so make sure that you build them with some kind of protection around them or put them inside your castle.
Because of the fact that they only break when empty, wood storages can last quite a while, and so will take up space for a while. Because of this, try to build wood storages in the empty grey zone between meadows; putting wood storages on meadows decreases your space for farming, and you may not get that space back until the wood storage breaks, which may take a while.