For Seniors: Get Apps from the App Store on Your iPhone 4S
Buying apps from your iPhone 4S requires that you have an iTunes account. After you have an account, you can use the saved payment information there to buy apps in a few simple steps or download free apps.
Tap the App Store icon on the Home screen.
At this point, you have several options for finding apps:
Tap the Search button at the bottom of the screen and then tap in the Search field, enter a search term, and tap the result you want to view.
Tap the New, What’s Hot, or Genius tab at the top of the screen to see that category of apps.
Tap the Featured or Top 25 button at the bottom of the screen to see which free and paid apps other people are downloading most.
Tap the Categories button to browse by type of app.
To install the free iBooks app, follow these steps:
With the App Store open, tap the Search button, enter iBooks in the Search field, and then tap the name of the app when it appears in the results list.
Note that when you first open the App Store, a message appears suggesting you download the iBooks app. If you already saw that message and downloaded it, feel free to download any free app in these steps, such as the Twitter app.
Tap the Free button for iBooks in the results that appear. (To get a paid app, you tap the same button, which is labeled with a price.)
The Free button changes to read Install (or, in the case of a paid app, the button changes to read Buy). Tap the button; you may be asked to enter your iTunes password and tap the OK button to proceed.
The app downloads; if you purchase an app that isn't free, at this point your credit card or gift card balance is charged for the purchase price.
Out of the box, only preinstalled apps are located on the first iPhone Home screen. Apps you download are placed on additional Home screens, and you have to scroll to view and use them.
If you've opened an iCloud account, you can set it up so that anything you purchase on your iPhone is automatically pushed to other Apple iOS devices and vice versa.