Upon starting WS Sports the login window below pops up. The first entry refers to the Database in use, the second is the Identification, which is computer-dependent and should not be changed. The last two entries cover the User and Password, by clicking OK the programm will be started.
If no branch has been selected on your computer yet, the window below will appear asking you to choose/create a branch. In case you need to change the branch on a computer, you can also access this window by Tools - Select Branches.
As a unique identification is mandatory to identify one's computer with a branch, it has thus been made clear why you're not supposed to change the Identification upon login.