How do you alpha/beta test an iOS app?

Here you go buddy:

https://developer.apple.com/library/mac/documentation/IDEs/Conceptual/AppDistributionGuide/TestingYouriOSApp/TestingYouriOSApp.html

A couple of broad pointers:

1) You can go either route and it will depend on what you're trying to achieve. For private distribution / bypassing the App Store, look into TestFlight. There are limits on how many people can test via this route so you need to decide if that's enough. If this is more of a B2B app, you can also look into the Enterprise license from Apple.

2) Some companies decide that they want the broader feedback of a larger audience and elect to distribute their app in a foreign app store before bringing it to the US. This helps to evaluate adoption, usage patterns, etc and make tweaks before bringing the app to a wider audience. I believe the Canadian and Australian app stores are popular testing grounds for this.

Testflight