How do you download apps

Start here:

Download apps and games from the App Store - Apple Support

Depends on where they are offered. If in the App Store, that is where you download them.

If not, then the developer's website.

Don't download from any of the software aggregating websites (CNET, Softpaedia, etc.).

Looks like NetSpend is only for phones...

https://www.netspend.com/prepaid-debit/features/mobile-app/