Hearing "there's an app for that" is not helpful if you don't know how to put an app onto your iPhone. Fortunately, Apple has made it fairly easy to download apps, both paid and free, from its App Store, so you can check the weather, play a popular game or perform thousands of other tasks.
Creating an Apple ID
Confirm you have an Apple ID. If you have bought music from iTunes or have an iCloud account, then those login credentials are used when signing into the App Store. If you haven't established an Apple ID, you can create one on Apple's website.
Sign in on Your iPhone
Touch "Settings" (on the home screen) and then "iTunes & App Store." Enter your Apple ID and password; once you've signed in, you remain signed in until you choose to sign out.
Browsing the App Store
Touch "App Store" on your iPhone's home screen. Use the icons at the bottom of the screen to find the apps you want. "Featured" are the apps that Apple deems the best new ones; "Top Charts" are the best sellers; "Explore" allows you to search under a list of categories; and "Search" allows you to find apps by keyword.
The Difference Between Wi-Fi and Data Downloads
You download apps either using your cellular data plan or by a Wi-Fi Internet connection. The disadvantage of data downloads is that they usually count against your minutes (depending on your plan), and too many downloads can really jack up your monthly bill. Also, Apple has imposed a 100MB limit on data downloads; files bigger than that can only be downloaded over Wi-Fi. Apps you download over Wi-Fi do not count against your data plan.
From the App Store to Your iPhone
Touch the price of the app (or the word "Free") to download and install an app. Then just touch "Open" (within the store) to launch it, or simply return to the home screen and touch it there.