I need credit card and I don't have one
Here you go:
Creating an iTunes Store, App Store, iBookstore, and Mac App Store account without a credit card: http://support.apple.com/kb/HT2534
Step 3 is important, no matter whether you do this on a Mac or an iPad / iPhone:
Important: Before proceeding to the next step, you must download and install a free application.
Important: Before proceeding to the next step, you must download and install the free application by tapping Free followed by tapping Install App.
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