I update libreoffice a 184.108.40.206 from 3.6* and I’m not able to set the default template. In 3.6 I didn’t have any problem proceding as said in this link.
Now I see the old template but I cannot do anything with it, there’s no action available (Calc pop-up window)
I think better take a look to the guide in:
I have to go to File → New ->Template tab Spreadsheets, select the template and then click on the button that appeared (as said in the pdf you link, page 19)
I tried importing a template in Calc version 4.2 and the template manager box remained empty.