I hope it works... just press the green flag and your username should be stored in the list. If the name is already on the list, it won't be used. If the cloud-storage is full, your name will also not be used.
NOTE: If scratch identifies you a a "new scratcher" or you dont even have a account, then this Project wont work for you. When does scratch identifiy you as a "new scratcher" and how to get rid of the status: https://en.scratch-wiki.info/wiki/New_Scratcher_Status
