If you set the in-app region setting as the United States, India, China, South Korea, and Brazil, you will get this "Task Center" section on the Personal tab.

In Task Center, you can complete the tasks, to earn Golds. Once you have a certain amount of Golds, you can go to the castmart to buy things, such as 1-month premium version, BOX tokens, etc.

Please take the following screenshots for your reference.