Hello my name is XXXXX XXXXX I will be happy to assist you today
So you never have setup and Apple ID before?
You can create an Apple Id by going to the following link. https://appleid.apple.com/cgi-bin/WebObjects/MyAppleId.woa/ <click link
Once you are there and you have created an Apple ID then you need to set your phone so it knows what Apple ID to use all the time.
You should be able to go to Settings then Store. Here is where you can log in to your Apple ID
Now you should be able to go any where and have it not ask you that question any more. Plus if you use another Ipod, Ipad, Computer you can use the same Apple ID and all your purchases and downloads will be saved.
If you need any more information on this problem just let me know. I am happy to help your more.
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Have a beautiful day