How do i change from blackberry to Iphone?

So my bud is selling me his Iphone.. I have a blackberry and i know that iphones don't have SIM cards, but like what do i do and where do i take it so i can change phones? Like Apple store or AT%26amp;T, or like best buy?How do i change from blackberry to Iphone?
iphones have sim cards

so if you have an at%26amp;t sim card, you can just put it in



http://www.youtube.com/watch?v=kir19QRGz

http://www.ilandvn.com/hinh/800px-IPhone

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