After plugin is installed you have to start initialization process. You have to be logged in administrator account first and enter in "Add-ons" view.
There are two ways to ways two do it. Either by clicking Configuration button in Manage add-ons view (note: button is localized below Vacation Manager plugin name).
...
Click next, and you should see view to configure first vacation type.
In the third step you can need to define a first Vacation Type.
...