After opening "National K Song", click the symbol behind "My, set your personal signature" in the lower right corner, click "Nickname", enter the nickname you want to modify, and then click "Finish".

The operation steps are as follows:

After opening the "National K Song"

Click on "My,

Click the symbol after "Set your own signature",

Click on "Nickname",

Enter the nickname you want to modify.

Click "Finish".