keep getting a message that says this apple ID has not yet been used in the iTunes store

Add, or verify your existing purchasing information on your Apple ID account with Apple. You’ll probably have to (re)enter your security code from your credit card, or enter the credit card and billing information if it’s not already recorded.

There are various ways to access this. From your iPhone, Settings > {your Apple ID info} > Payment & Shipping

Change, add, or remove Apple ID payment methods - Apple Support

stuck_in_cincy wrote:

...You have to enter payment and billing info even if you don’t ever plan on buying anything...

Create or use an Apple ID without a payment method - Apple Support

That should (will) allow access to free items.