You can access your warehouse through Keeper Daru in town.

There's no storage fee for storing items and Gold, but it costs money to retrieve items.

■ Warehouse Info

 - Storage Capacity: 20 slots by default, expandable up to 300 slots with Gems

 - Item Retrieval Cost: 1,000 Gold per item type (e.g., 5 types of items cost 5,000 Gold to retrieve.)

 - Gold Withdrawal Cost: 1,000 Gold for any amount

※ The expanded warehouse space is applied to all realms (servers).