Getting apps

First, check if the device is connected to the internet. Then

If you can't make purchases or update apps, including free apps, you need to update your payment method or add a new one. If you already verified that a payment method is available in your country or region and you're still having trouble, learn more.

What error message are you receiving?

I’d also recommend taking a look on here as it may help you: https://support.apple.com/en-gb/HT204266#download