In Entourage prefs, go to Sync Services and turn on syncing between
Entourage and iCal.
Right idea but some additional steps might be helpful:
1. Create a new calendar in ICal name 'Entourage', but without the
quotes
2. Select all your events in the lower area of ICal (in the list below
the actual calendar)
3. Assign the 'Entourage" calendar you just created as the calendar
for all the selected events
4. Now turn on Sync Services in Entourage and choose to replace all
the Entourage with ICal events, unless you want to keep existing
Entourage events. If you do, choose merge instead. However if you do,
the existing Entourage events will appear in the 'Entourage" ICal
calendar.