Right click on the light and it will bring up the properties tag for the entity or light in this case. The default light range is "500". If you increase this number it will expand the range of your light. If you are going to use a light with a large range, you will want to change the color of the light to be pretty dark to get a better distribution across your scene.
I would strongly recommend reading the user manual as it will answer most of your initial questions as well as make you aware of features that you probably don't know exist yet.
Best,
SREALIST