Don't worry about having "too much light". That is easily fixed by moving the light farther away or putting in a smaller wattage of bulb.
Main Light = just what the name implies, it is your main source of light and helps establish your exposure.
Fill Light = usually placed on the opposite side of the main light. The fill light is used to fill in the shadows created by the main light.
A typical light set up using just the main and fill light is as follows. Set up the main light at a 45 degree angle from the subject. point the light away from the subject shooting into an umbrella. set up your camera on a tripod. set up the fill light beside the tripod on the opposite side from the main light. point the fill light away from the subject shooting into an umbrella. To vary the exposure using this setup, you can either change bulbs or set the lights farther away from the subject. check how the shadows are falling onto your subject. Adjust your lights to vary the shadows. A good starting point would be set your camera up on a tripod the distance you need to be for the composition you want the photo to be. Set up your main light about 42" from your subject on the right side of your camera about 12" higher than your subject pointing down on your subject. Place the fill light beside your camera on the left side even with your lens. With both lights on, take a meter reading to see what the exposure is. Lets say that the exposure meter says f/8 with a shutter speed of 1/30. The f/8 will give you a great depth of field to keep the cat in focus but the 1/30 shutter speed will give you blurring if the cat moves. How do we fix this? Move the main light and the fill light closer to the cat. If the exposure says f/8 and shutter speed of 1/500 then you would want to move the lights farther away. If the cats wants to move alot, then I would want a shutter speed of 1/200 or 1/250. If the cats don't move too much then a shutter speed of 1/60 or 1/125 might work.
Now for your homework assignment: Acquire 2 stuffed cats. one black and one white. These will be your subjects while you learn to read light. Set up your background and pose both stuffed cats. Set up your camera on a tripodat the distance that you like the composition you see in your viewfinder. If you do not have a tripod, then set the camera on a stool for now. Set up your main light as I explained earlier. watch the cats. move the light closer to the cats, see the shadows change and the brightness of the scene change? move the light farther away. watch how the shadows and the brightness change. put the light back at 42". leave it on. set up your fill light as I explained earlier. see how the shadows gets filled in? move the fill light closer to the cats. see how the fill light fills in the shadows and brightens the shadowed part of your cats? move the fill light farther away from the cats. see how the shadows gets darker? You just learned about how to control light. Now tell me the results you saw with the light placement of the main and fill lights.
If you do not understand something I said here, then give me a call at 907-262-5642 and ask for David. Sometimes it is easier to talk and explain than it is to write and try to explain. Plus the feedback is immediate.
I will teach you about light and how to controll it to suit your needs.
Please keep in mind there is a 4 hour time difference between NY and AK. Please do not call at 8am your time as that will be 4 am MY time.