Do you mean change your name / public name? If so, you can do this from your Atlassian profile.
For example, to do this from this question:
If you cannot modify your full name - look at what the pop-up reads when you hover over the field. It might be your full name is managed centrally if you are part of a wider organisation which manages user profiles via LDAP, etc.
You should also be able to access your profile via: https://id.atlassian.com/manage-profile/profile-and-visibility
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