How do I shape my eyebrows? Any good kits?

I'm 17 and have never done this, My friends have told that I just need to trim, but I want to shape them. Are there any eyebrow kits for beginners at walmart or target? Also I'm a brunette. does that have something to do with it? Also if I tweezed places that shouldn't of been tweezed can that be fixed? Also any tips on how to get the perfect eyebrows for me? Thanks for all that help