Collecting Esper, the second currency in Fableborne, is an automatic process, and you don’t need to do anything specific to acquire it. You can increase your Esper storage limit by constructing and upgrading Storages within the game. Gain Esper by leveling up, claiming your Daily Bonus, and successfully defending in battles. Just check your Battle Log to see how much Esper you've gained each time your base was attacked.