How to download and use third-party apps on iPad

Someone_with_an_ipad wrote:

I have searched a-lot for an answer, but I cannot find anything. Does anyone know how to help?

Start here:

If you can’t download or update apps on your iPhone or iPad – Apple Support

If you are experiencing difficulties with adding or removing Apps to/from your iPad, you need to check your ScreenTime restrictions:

• Settings > Screen Time > Content & Privacy Restrictions > iTunes & App Store Purchases > Adding Apps - ensure that this permission is set to Allow
• Settings > Screen Time > Content & Privacy Restrictions > iTunes & App Store Purchases > Deleting Apps - ensure that this permission is set to Allow

You are going to have to be a lot more specific. The App Store contains thousands upon thousands of 3rd party apps. Not everything there is produced by Apple. As a matter of fact, they only produce a handful of apps. If you are asking about installing content from outside the App Store, that is only possible via MDM profile or jailbreaking your device, which, no-one here in the forums will give you details how to perform as it is not an advised action.

Did you setup a payment method for all of the online Apple Stores, in the Settings app, under your large Apple ID panel under Payments and Shipping?