Hi,
You have to type in the flight plan into the program yourself. Say you're flying NZWN - NZAA. (Not sure if you know about flight routes but the Wellington-Auckland goes via the airway "WN vor, H277, and AA vor")
So you would type into the blank space "NZWN WN H277 AA NZAA" press Add, select the current runways, and the flight plan should appear in the space above.
You can enter SID's and STAR's at any time. So after you enter the route, click on the airport you are flying out of and click the "SID" button. Unless you have you have a current
AIRIC cycle version (payware) installed, there may not be any (or any up to date.) Select the appropriate one and press OK. The way points of the SID will be added in order, below the airport entry.
Oh and after you program the FMC, you want to delete the airport's (your flying out of) VOR from the list. Otherwise after takeoff, it will tell you to turn around, and will fly you over the airport's VOR, and then continue on your course.
Add STAR's the same way, as you approach your destination (or whenever), but instead, select your destination airport on in list and select STAR.
Hope this helps, if it doesn't make sense ask again.
Nick