How to make my used iPad 4 compatible with iTunes and download apps?

Update support for iPad4 ended September 2017. The final iOS releases for this model were iOS 10.3.3 (WiFi Only models) and iOS 10.3.4 (WiFi & Cellular). iPad4 cannot be updated to any later major version of iOS as it lacks the minimum hardware requirements needed to run more recent versions. The 32-bit platform upon which the iPad4 is based is obsolete.

Developers have dropped all support for 32-bit devices - and have withdrawn all 32-bit Apps from the Apple App Store. Withdrawal of Apps supporting older models of iPad is making their utility and usefulness significantly more limited. Once compatible versions Apps are withdrawn, you’ll not be able (re)download or (re)install them.

If Apps that you need to use now have higher minimum iOS-version requirements than your iPad is capable, your only option is to replace your iPad with newer model. Of current models, even the entry-level iPad 10 supports current iPadOS 17 - and has hardware specifications and capabilities that vastly outperform an old iPad4.

For information, here is a list of the highest version of iOS supported by the older models of iPad (for simplicity - “generations” are shortened to a number) that are restricted in their ability to be updated:

32-bit devices (obsolete)

iPad1 - iOS 5.1.1

iPad2, iPad3 and iPad mini1 - iOS 9.3.5 (WiFi Only models), iOS 9.3.6 (WiFi & Cellular)

iPad4 - iOS 10.3.3 (WiFi Only), iOS 10.3.4 (WiFi & Cellular)

64-bit devices

iPad Air1*, iPad mini2 and iPad mini3* - iOS 12.5.7

iPad Air2, iPad mini4 - iPadOS 15.8.2

iPad5, iPad Pro (9.7"/12.9" first generation) - iPadOS 16.7.8

(*) obsolete

Newer models are all able to be updated to the current version - iPadOS 17.5.1

• iPad Pro 13" (M4)
• iPad Pro 12.9" (2nd generation and later)
• iPad Pro 11" (1st generation and later + M4)
• iPad Pro 10.5"
• iPad Air (3rd generation and later + M2)
• iPad (6th generation and later)
• iPad mini (5th generation and later)

Assuming you were able to set up the iPad and the issue is solely that you can’t use iTunes or download anything it is likely because that iPad uses a very old iPadOS version. Most if not all apps at this point no longer support that version. Also (and most important) that iPad is now on the obsolete list assuming you have properly identified that the iPad you have is indeed the iPad 4 (ie iPad 4th generation).