Hi Marcelo,
The work orders should show on the calendar when they are created. For instance, if you create a series and make it occur each day this week, all 5 activities will show on the calendar. Is this not what you are seeing?
I'd also check the some settings on the work order activity type. This can be done by either clicking the ... next to the activity type dropdown on the new activity screen or by going to Customize > Screens and clicking View on CRM_ActivityTypeList. On this screen you'll see settings for "Show on Calendar" and "App specific". Depending on how these are set, you may or may not be able to see the work orders.
- Adam