Go to Wizard/Events/Respond To Events. Choose from the list 'sensor is triggered'. For the device, choose the motion detector. In the 'time of day', put 'NIGHT'. then in the 'commands to send' section below it, chose the light plus 'on'. Next add a command going to DCERouter, "Delay", put 240000 in for the delay (it's in millseconds), and then choose the light and choose 'off'.
There are 2 pieces that are still missing. 1) Day/night. With .18 it assumes if it's before 8am or after 8pm it's night. However, we are adding a module that will use your ip address to get the longitude/latitude and calculate sunrise/sunset appropriately. And there will be a device data in Event_Plugin that allows you to specify a sensor to be used for this calculation instead (ie your daylight sensor). That hasn't been done yet, though. They're both quite trivial to do--they'll just be functions in Event_Plugin. We just haven't gotten to it yet.
2) The other piece that's missing is resetting the timer if motion resets within 4 minutes. We need to add another command for DCERouter called 'reset processing event hander', or something. Again, not a biggie. Just haven't gotten to it yet.