Roberto,
You must first lock your flight in the "Propilot" of the web site.
For now you should see your aircraft parked at EGLL, and it should let you lock it BUT the "available flights" list should be empty (until tomorrow, when the first leg will appear... by magic of course).
Also, in order to use the new aircraft and flights, you should use the "update" function on flight logger.
Only after you perform these two tasks, you can use the "Propilot" button on flight logger and this will initialize the flight for you.
Hope this helps
Andrei