1, open the class optimization master, select the address book at the bottom, and click the+sign in the upper right corner.

2. Enter the interface and fill in the Xixi number of the class.

3. Enter the interface. You can fill in your child's name, or you can find your own child from the class and choose for yourself.

4. Select from the class to enter the interface.

5. After finding your child, select it. The "Apply for Class" button at the bottom turns blue, and then click it.

6. After joining, you can choose to join mathematics.