To edit the user, you must perform the following steps:
1. Choose "Manage users" in the main menu
2. Click on the user you are interested in (in the area where there are no buttons)
After that, the editing page will open.
Keep in mind that you can not change username.
Click button "Save" ( in action menu) to save it

Then you can click "Back" ( ) to return to the previous page.
How to configure the user is described in detail in the article "Adding new user"