How to Delete an App from Your iPhone
You can delete an app from your iPhone in two ways: in iTunes on your computer or directly from your iPhone. To delete an app in iTunes, click Apps in the source list and then click the app’s icon to select it and then choose Edit→Delete or right-click (or Control-click on a Mac) the app's icon and choose Delete.
Either way, you see a dialog asking whether you’re sure you want to remove the selected app. If you click the Remove button, the app is removed from your iTunes library, as well as from any iOS device that syncs with your iTunes library.
Here’s how to delete any third-party app on your iPhone:
Press and hold down any icon until all the icons begin to jiggle.
You can’t delete any Apple apps that came with your iPhone.
Tap the little x in the upper-left corner of the app you want to delete.
A dialog appears, informing you that deleting this app also deletes all its data.
Tap the Delete button.
Deleting an app from your iPhone this way doesn’t get rid of it permanently. The app remains in your iTunes library until you delete it from iTunes. Put another way: Even though you deleted the app from your iPhone, it’s still in your iTunes library.
If you want to get rid of an app for good and for always after you delete it on your iPhone, you must delete it also from your iTunes library. Even then it’s not really gone forever because you can download purchased apps again for free.