If you'd like to change your email or display name, do the following:
1. click / tap your profile icon in the top right and then Account Settings;
2. to change the display name, just replace the old one and click Save;
3. to change the email, click Change Email, enter the new one, and click Save;
⚠️ Changing username is not currently available, though the feature might be added in the future. The only option would be to create a new account with a desired username ⚠️