The iPhone, which is manufactured by Apple, features miniature mobile applications called apps. The iPhone comes with native apps, such as Mail and Safari, but you can also download free and paid apps from Apple's iTunes Store. The iTunes Store works both with computers and the iPhone, but apps purchased on your computer must be synced to your iPhone. Use the USB cord that was included with your iPhone to sync files and apps from your computer to your iPhone.
Open iTunes on your computer. If you do not have iTunes, download a free copy from Apple's website. iTunes is available for both Mac and PC. Turn on your iPhone and enter your passcode if you have one to disable the lock function. Connect your iPhone to your computer using a USB cord.
Click your iPhone device icon in the left menu bar of the iTunes application window. Click the "Apps" tab in your iPhone information window.
Check the Sync Apps box, then select the apps you want to transfer to your iPhone. You can view apps by name, kind, category, date purchased and size by using the drop-down menu tab. Apps that you leave unchecked remain on your computer and are not transferred to your iPhone. Check the Automatically Sync New Apps box to automatically copy your new apps every time you sync your iPhone.
Organize your apps by dragging the app icon and dropping it to the location you desire. You can change your home screen apps and create multiple pages. To move an app to a new page, drag the app icon and drop it in the page icon. To organize a page, click on it and drag your apps. To create a new page, drag your app icon to the gray rectangle, which represents a blank page.
Create app folders to organize your iPhone if you are on iOS 4. iOS 4 is compatible with the iPhone 3GS and iPhone 4. Drag one app icon and drop it onto another app icon that you want to include in the group to create an app folder in iTunes. Type a name for your folder into the box that appears. Drag and drop icons into the folder to add more apps. Each folder can hold up to 12 apps.
Click the "Sync" button to apply changes and transfer your apps to your iPhone. Allow your iPhone to finish synchronizing before attempting to disconnect. When you see the "Okay to disconnect" message on your iPhone and in iTunes, you may unplug your iPhone.