Re: So I got an old iphone 6+
Phone may need updating to the newest compatible iOS version: (Eg: via Settings > General .> Software updates)
About iOS 12 Updates - Apple Support says iOS 12.5.7
"This update provides important security updates and is recommended for all users."
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Re;"created a apple id..the problem is it wont let me sign into the app store without making a purchase in itunes "
Check you are signed in (to your device) with the Apple ID you will use for the App Store, (if not already done).
Sign in to your Apple Account - Apple Support
Because you created a new Apple ID:
Apple requires we have a payment method listed in an Apple ID account for the first time we use the App Store or iTunes., even if we only download free items. {Seems an actual purchase is not necessary)
See which payment methods Apple can accept in your country or region:
Payment methods that you can use with your Apple Account - Apple Support
How to Add an Apple ID Payment method:
Add a payment method to your Apple Account - Apple Support
You may need to allow 24 hours for updates to come into effect.
or
Restarting your device may help you view recent changes.
What to do: If you need to change or update your Apple Account payment method - Apple Support
or
How to delete an Apple ID payment method:
Remove a payment method from your Apple Account - Apple Support
IF needed: How to: Get a verification code and sign in with two-factor authentication - Apple Support
Get a verification code and sign in with two-factor authentication - Apple Support
More help or support:
(There are "Get Support" links as the bottom of the websites (links below) (ie online chat, phone, eMail)
Apple Account support / help website: Apple Account - Official Apple Support
For iTunes support and more:
Subscriptions and Billing Website: Subscriptions and Billing - Official Apple Support