Your Issuu account username is part of the URL of your Issuu profile -- where you can see all of your uploaded content (issuu.com/username). Your username can be either chosen by you when you create an Issuu account or auto-generated if you signed up via one of the social channel links.
Changing Your Username
Unfortunately, at this time it is not possible to change your Issuu account username.
NOTE: When setting up the new account, please make sure to use the email sign up option, as this will allow you to manually choose a new username (see screenshot below).
Any statistics that were associated with a publication on the old account will not be transferred to the new account when you re-upload them.