Getting lighting effects around an arch

[Darth_Sceptaurus]

Hi all,

I am trying to get some highlights/shadows going on around this arch on my doorway, similar to what I have on the trim you see above.  I am not finding any simple way to do it, and in fact with every way I have tried I've ended up running into roadblocks.  Can anyone recommend the best, easiest, or most straightforward way to do this?