No matter the type of Actor you are using in your level - be it a light, a Static Mesh, a Particle System Emitter Actor, or anything else - you will need to know a few basics on how to create and manipulate them in your scenes.
This involves a few integral tasks: placing Actors, selecting Actors, positioning Actors, and modifying Actors. In other words, to create a level, Actors will be placed into a map, moved around to create an environment, and their properties will be modified to cause them to look or behave appropriately.