led cathode to ground, led anode to transistor base... transistor collector to pic pin, transistor emitter to ground... either use a pic pin with an internal pull-up (like portb), or use your own weak external pull-up, connected to v+
my suggestion is just something fast, which could be scrapped together from parts laying around my work bench and provide a simple Light/Dark logic state. on the other hand, you could abandon the transistor all together, and just connect the leds' anode directly to an analog input on your PIC, the LED will output a voltage between 0 and ~1.5v in relation to the intensity of the light it is 'seeing' - you could take this data and do what you want with it, like adjusting the light/dark threshold... for example is it overcast, or did the sun really set? and conversely, was that just some passing by automobile headlights, or did the sun rise?