I watched a side light (parking light) being replaced. The bulb holder is just pulled out from it's housing, the bulb replaced, and the unit pushed back into place. It is reached from inside the bonnet.
You first have to purchase the correct light bulb for your Peugeot 207. The next step is to remove the bolt that is holding the light bulb cover in place. Then, remove the light bulb cover. finally, replace the bulb.