Richard,
Make sure iCal>View>Show Info is selected.
1. Create a "New Event."
2. In the Info window: Click on "repeat" (None) This will reveal a drop down menu which will allow you to select Custom...
3. In the Info window: Select "Frequency" (Weekly) Every (2) week(s) on: Choose your day and click (OK)
4. In the Info window: Click on "alarm" (None) This will reveal a drop down menu which will allow you to choose the method of alarm.
;~)