To modify user data go to User - Management --> User - Overview in the main menu.
Fig. 5.2.2 - Modify user
You will see a list of all user profiles. Click the 
-Button next to the user you want to modify. This opens the same mask as creating a new user, allowing you to modify user data.
Fig. 5.2.2.1 - Edit user data
Confirm your changes by clicking the "save"-button. A summary lists all the changes done.
Fig. 5.2.2.2 - Modified user data
Clicking the "back"-button takes you to the user overview again.