It is not currently possible to change your npm username. You'll need to create a new account and migrate the data to the new account manually.

1. Create a new user account with your desired username
2. Transfer your packages to your new account.
3. If you are a member of any organizations, ask the organization administrator to invite your new account to the organization.
4. Delete your original account. Note that this is permanent, and after 30 days, this account name is available for other people to claim.