You can change your name in the user settings on platform.openai.com by going to User -> Settings -> Personal profile -> Name.
Note: Changes you make to your name on platform.openai.com may take up to 15 minutes to be reflected in ChatGPT.
Link: https://platform.openai.com/account/user-settings
The following are the settings:
ChatGPT
Change your name on platform.openai.com and refresh ChatGPT to see the update.
Requirements
A name value is required.
It must be 96 characters or fewer.
It may contain only letters, certain punctuation marks, and spaces. Numbers are not allowed.