Requirements: level 45+

To access the activity, click on the icon in the right-hand menu.
 

You need to click on citizens with a question mark above.  

Clicking on a question mark will open a citizen's task.

If you agree to complete this task, click the OK button.

You can reject the task by clicking the red button. If you do that, you will have to wait 3 hours before a new task arrives. However, this waiting time can be skipped for superbucks. 

Thus, you need to complete the tasks given by citizens and accumulate special coins. The more coins you accumulate during the activity, the more rewards you get.

In this tab, you see the citizens that need your help and the number of coins they will give you for completing their task. The tasks have no timer.

Clicking on a blue button will open a window with a task from the citizen.

As soon as you complete a task, a new citizen with a question mark will appear in the city.

Completing tasks will eventually give you access to bonus tasks. 

These tasks have a timer and offer an increased number of coins for their completion. You cannot reject a bonus task.

If you do not manage to complete a bonus task within given time, you can either reject it or complete it for superbucks.

You get rewards for accumulating special coins. You can see the rewards here: 

Purchasing the Gold Gift Key will give you access to the Golden Gift and bring you more rewards.

The main reward:
 

You must collect 15 special coins to enter a rating.