I have an iPhone 4. I have created the Apple ID. Now when I try to download anything from the App Store and I log in with my ID and password, I see the message "this ID has not been yet used". What should I do? I have no more knowledge about these procedures.
Download the latest version of iTunes for your Mac or PC. Install it and log in with your Apple ID. If it presents the terms and conditions for Apple ID, accept them and follow the instructions on the screen.
If you are asked for credit card information, and you don't want to provide it (maybe you will only be getting free apps), you will have to register for a new Apple ID, this time creating it directly in iTunes. That is, the iTunes program on your computer, not on the phone.
Note! Do not use a web browser to navigate to https://appleid.apple.com and create your Apple ID. You must create it inside iTunes, and you must click on one of the free items (like a free song). Sadly, that's the only workaround in case you don't want to provide credit card information.
These two web resources might be helpful.
If you haven't created your Apple ID, follow these steps to create an Apple ID and store account at the same time, without adding a payment method.
For iOS era devices (as was true for computers initially), the obvious case for not being able to talk to the online store is network issues. The tap should take you to the page to enter payment and address or complete the account setup for your AppleID. You can manually enter that following the links below if you want.
If you can’t take your iPad (or other device) to a new network and retry, then setting up your account on iTunes or a web browser will let you know if the issue is on Apple’s side (contact store support), on your network side (work with someone that knows network after restarting everything).
Once you’re sure the account is good and the network is good, erase all content and settings and try again to set up the iPad.