Still trying to figure this thing out!

Either I'm dumb or not as computer savvy as I would like to think I am.  I just don't understand why I changed my background to something cute, but part of my old background is still showing up.  I see everyone with these cute blog backgrounds and I tried to do what I was told to do, but I'm still so confused.  HELP!!!!!!  How in the world do you get a big pic on the top of your blog?  I think I have checked under every tab on this thing and I can't find anything.  I think I need like a Blogging for Dummies crash course.  Maybe I can go buy a book somewhere...yeah right, with 3 kids I don't have much spare time to read anything.  One of these days I will figure it out, just not today...I'm too frustrated.  In my mind, if I can't figure it out quickly, then I'm not going to sit and mess with it for too long...too many other important things to do, like getting Delaney ready for soccer practice, cleaning up my house for the "umpteenth" time today, etc.