Before you start, you need a WEBKiosk and in the collections in the WEBKiosk should already exist and be linked to the WEBKiosk.
How to do this you'll find out here. 

Open parallel in a new window or tab your WEBKiosk to control the process.

Go to "My WEBKiosk".

Click on "Tasks" - "Edit Design".

You are now in the backend of the WEBKiosk.
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Scroll down until you reach "Document". Depending on how your WEBKiosk is designed, you will usually have 1 Document Widget.
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The Document Widget is linked to the collections. 

 1 collection = 1 document

Delete or remove the existing widget.
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Use the "+" to add another "Document Widget".

Select one of your collections in the "Settings" tab under "Collection".

*Show all Collections means that all your collections are displayed - no particular order! In this case 1 widget would be enough.

​Save & Close.

Repeat the process until you have the same number of "Document Widget" as collections (which are linked to the WEBKiosk). 

Go to the WEBKiosk-link you opened at the beginning.
So you can check if the order you want to have is correct.

If it's not correct, you can drag and drop the widgets in the backend.