To set "Look in Everywhere" in the "Look in" search textbox when adding a user to a group follow the steps below.
1. Open Adaxes Web Interface Configuration.
2. Choose the appropriate Interface type.
3. Click "General" Tab
4. Click "Configure Home Page Actions..."
5. In Actions Pane->User Management, right click "Add to Group"
6. Click "Edit..."
7. In "Edit Home Page Action" dialog box, click "Target Object Selection" tab.
8. In "Perform on the selected AD objects" section, uncheck "Allow selecting only AD objects located under a specific OU or container"
9. Click "OK"
This should set the default "Look in" search textbox to "Everywhere"