Why wont my car start/ Turn Over and makes clicking noise after.... Is it the Battery, Starter, Alternator?

I have a 2002 Mercury Sable LS Premium 35,000 Miles and has a half tank gas. It worked fine the night before then in the morning I went to go start the car and it wouldn't start I had a friend come and try to jump me and that didn't work.... It doesn't turn over when I try to start it , and it makes a clicking noise after I try to turn it over and still makes the clicking noise when I take keys out, the lights turn on but are very dimmed, the power locks, windows, and seats don't work either when I try to turn it over and radio doesn't work too just shows the clock for like 10 seconds. I bought the car 2 months ago only put 1,000 miles on it tops.... They told me when I bought it that the battery was basically bran new.... I am just wondering what are peoples ideas about why the car isn't starting any help, tips, info is greatly appreciated thanks.......