the display name can be changed under Store Settings. When you're logged in, click on your name (top right) to open the go to the drop-down, click on 'My Store', then in the tabs below you should see 'Store Settings'. You can also click on https://www.tindie.com/stores/settings/
Please make sure that you fill out all the details on the store settings page, including the returns address.
If you have any other questions, you can ask the community here, or email our team at firstname.lastname@example.org.