Click on the three lines in the upper left corner, then a menu will appear from the left, select the top circle (if you have set an avatar, the circle will be your avatar, if not, it will be blank ) Anyway, just click on the circle and you will go to the personal homepage. The top is your nickname and the bottom is your avatar. Then click the icon circle and you will go to the personal settings page. Just click on the nickname to modify it. Click on the avatar circle. It will display "Take a photo" or "Select from album" to choose one method.

Hope to adopt it! ! Thank you