Please try Setup-->Libraries-->Library Service.
Select the Padstack tab at the top of the GUI. ( Operation Import/Import from: Library database)
You now should see on the left all your Padstacks in the Central Library, by selecting the one you search for and pushing it to the right side you can copy them to your design database.
After that you should see the copied Padstack in the via definition.
All things that are not in the Layout template and have no schematic instance must be added via Library Service.