Kerkythea?
Insert (on the menu) -> pick a type of light.
It is created at the camera location, then you can move it later; and set the strength, color, etc.

Settings -> Sun & Sky.
Set the location, date, and time of day. [Press Next]
-use the pulldown menu. 'Physical Sky' gives you a preset gradient color. Intensity is how bright overall the sky is. Turbidity is sort of like rotating the gradient, to make the dark/light areas move up and down.
-There are also options in the pulldown to insert image backgrounds. Normal photos can be used w/ 'Background xxx', the 'centered', 'tiled', and 'fit' are just how the image is shown.
-'Spherical Sky' and 'Hemispherical Sky' is for panoramically transformed photos, you can use .jpgs, .bmp, and so on for that; and you can also use .hdr images too (HDRI, radiance file, made from assembling multiple exposures). When FG (Final Gathering) is activated, then the sky color/image will impart a tint onto the scene; depending on sky's intensity and turbidity. .HDR can be overwhelming, and there aren't any real controls for it in Kerkythea. If the radiance file has been properly tone mapped, then it is all right.

Settings -> Scene -> Global Settings
Ambient Lighting - a value that tells the renderer what percentage of material ambience to calculate. Probably not a good idea to use this until come to terms with the standard lighting.
Volume Lighting - When activated, calculates volumetric refraction and scattering through volumes (like light through fog); controlled by the global fog settings below.
Global Fog:
 - Emmitance - causes the fog to generate illumination.
 - Absorption - How much illumination the fog absorbs. It is z-depth buffered (that means that areas are thicker than others and absorb more light). This setting also determines density of the shadows cast by the fog.
 - Scatter - The color of scattered light
 - Scatter Density - How much light gets scatter vs. how much simply passes through.
Scatter takes very long time to render. Absoprtion is not too bad. Emmitance is not much time.

Render -> Setup -> Global Illumination

• Photons are for bouncing luminosity around the scene. 'Shooting Depth' is how many times the photon will bounce before expiring (It also becomes weaker with each bounce). Use the 'specularities' check box when you want the photons to form specular phenomenons. 'Mesh detail' makes the light bounces coincide with the mesh more accurately. '1' should be sufficient.
• Caustics is refracted and reflected light patterns (like the nephroid patterns you see around water from time to time, or light shining though glass). Rather render expensive, "pseudo-caustics" is fake ones that can added as wanted. 'Photon mapped caustics' are optical, and only happen under the optically correct circumstances. "Density' is how many 'rays' are calculated, higher numbers is better (but takes longer to render).
• Final Gathering bounces color. i.e. White light hitting a red wall will be tinted with red when it bounces. It can also make surfaces self illuminating, or actually emit luminosity. 'Rays' is number of calculations. 'Accuracy' is, well, accuracy ;). 'Gathering Depth' is how many times color will be imparted during a light bounce. 'Trace Depth' is number of bounces + number of refractions. The check boxes are which optical phenom. that the FG should account for in the render.
  'Moderate' GI setting in Kerkythea are pretty good; except I would use 'many' photons.
  Whatever you do, don't set FG accuracy to '0.0 - Perfect'...:scared:

Friends don't let friends use booleans.