Call up Nero CoverDesigner...
->A window "New Document" will appear

Select any Template.
->The Design area will show up.

Call up "File > Paper Stocks..." from the menu bar.
-> A window "Paper Stocks" appears.
Highlight "User defined Stocks".
Click "Add Stock"
-> A new Stock is added (called Stock 1).

Highlight Stock 1.
-> You can change the name of the stock to your liking.
Check/change Width/Height to the values as you like: Width: 210.200mm Height: 297.300mm
Set "Feed paper as:" to "Portrait"
-> The preview of the paper stock should show a square design.
Click "Add Item"
-> a context menu appears

Choose your items. I'd like to click on "Disc" (Second but last item)
-> a greyed out disc appears in the preview, aligned to left and top of the square.

Highlight "Disc" in the left hand window.
-> The disc in the preview will change its colour.

Now adjust the values for disc size:
Outer radius: 58.500 mm
Inner radius: 12.000 mm *** This gives maximum disc coverage ***
- > Inner and outer radius can be adjusted according to the target discs you use. Simply measure the diameter of your discs and divide by 2 to get the proper values for these entries.

Now adjust the values for the Position (X/Y)
16.00mm / 8.750mm
-> The disc in the preview will move to the correct position.

When you have finished click O.K. You can now use your own paper stock.