When your Club's Task meter reaches 100%, a checkmark will appear to the right of the Reward amount showing your Club has completed the Task to earn the reward. Everyone in the Club will be able to receive the Reward.
To collect the Reward, tap the Rewards button on the top left of the Club Home Screen. The badge icon shown on the button will let you know how many Rewards you have available to collect.
To collect your reward, tap the Claim Reward button on the Club Rewards Screen.