You can delete lights very easily. Look at your light panel [usually top left]. You'll see a number of small icons underneath it, these are Light properties, colour, and "delete". Select the light you want to delete then click on the icon that looks like a "bin". You'll get a please confirm delete type message, click ok and it's gone. I had problems with lights when I started and like yourself used preset ones from various sources, they're not ideal though and you can't always get the effect you really want. Now i do all my own and generally what I do is; look at your scene and see how you want to light it then add say a sinlge light and play with it's position, height, type, colour etc. and then add more to get further effects until you're happy with the effect you want. Hope this helps!

Injustice will be avenged.
Cofiwch Dryweryn.