I will explain the following: - The editable functions of the lights. - Placing lights in the correct way.
If you followed the Video Tutorials you should know how to get to the Edit window. If not I suggest you follow these Tutorials before beginning.
When you selected the light bulb you'll see this window pop up on the right side of your screen.
I shall explain these in short abbreviative answers.
Origin: Also know as the XYZ Position of the Entity, you can change these manual but the gizmo is usually more preferable.
Angles: The Rotation of the Entity somewhat useful when you're in a pinch, but the editor is simple enough so you don't need to do the numbers.
Color: You can change the color the lighting is eminating, it has RGB Values and uses a simple color pallet or you can choose from a slider.
Max Distance: This is the max distance the lighting will emit, in the viewport you can see a blue circle surrounding the light bulb, you can select that and move it. It will have the same function as the numbered one.
Intensity: This is used to define the intensity of the light, higher will result in a sharper and lighter light, the lower the more duller it gets. Default is 5.
Random info: The really useful Realtime Lit Viewport Simulation is very important, without it you wouldn't have it easy placing lights. Use this mode alot if you want to position your lights correctly.