.. How do I light this new area?

Remember how you lit the first burial chamber? This one works the same way. Mostly.

Walk past the black cat statues and look for a lamp fixture in the left wall, then add lamp oil and use the lighter.

The resultant mirror puzzle is the same general idea as the last one -- the light reflects off a series of mirrors until it hits the last light --

-- except this time you have to place the six mirrors yourself. No biggie; in fact, you can do it using only five mirrors.

To place a mirror, pick it up from the stack at the right and put it in one of the available holes. If it's tilted the wrong way, move the mouse a little till it turns into a circular arrow, then click to turn the mirror.

If you're stuck, here's how I placed the mirrors: