Hi Peter. Are you talking about the running lights or the interior lights?
If you're talking interior lights then don't worry, we've all been there and it is a bit tricky (and almost as tricky to explain )
The curved plastic light covers are held in at each end by the grey half round end caps (one has the light switch on it). Eventually you'll have to very carefully pull the bottom of these end caps away from one another to remove the light cover.
However, before you do that you'll have to remove the mesh grill strip (which is about 20mm wide) that runs along the whole length of the curved cover. It all can be just as tricky to put back together so look at it closely as you remove it. The grill section has a small in turning lip along the top of its length and you have to gently squeeze the curved cover together and at the same time pull the two end caps apart and the mesh grill should drop out.
The curved cover which is also held in by two outward turning lips can then be squeezed together and removed in the same way.
It's a bit tricky and the mesh strip is the key to it all. Hope that makes sense and I've got it right.
While on the subject of replacing interior bulbs many of us have replaced them with flat LED's which make a heck of a difference.
I'm sure someone has a link to where to purchase them somewhere but to be able to replace the existing bulbs, about 5 mm will have to be cut off the thread of the two bolts that hold the light fitting onto the underside of the overhead lockers. This is because the replacement flat "old penny" size LED's foul with the "through" of the bolts.

Exterior rear light fittings. You'll notice that at each end of the reflector block there is a square section with what looks like a thumb print in it. Squeeze the ends together using these indents and the reflector cluster with come off. The front running light covers are just a push fit held in by a rubber "O" ring.
Randa