First, you need to choose a picture that will stand on the lock screen or in the main menu of your phone. Pay attention to the dimensions of the selected image. For iPhone 3G, 3GS, 4 or 4s will fit the 640 by 960 pixels, but the iPhone 5 needs little more than Wallpaper - 640x1136 pixels. In the Internet there are many directories of images already selected size.
If you downloaded the image to your computer, transfer it to the phone via iTunes. Download this software from the official Apple website and then install it. When you connect your phone to the computer, the program will open automatically. In the upper right corner you will see a button with the name of your phone. Click this button and navigate to the "Pictures" folder. In the opened tab, select a folder in which there is a future saver. Next, click on the "Sync" in the lower right corner. In the Photos app on your iPhone should appear in the folder "my computer", which will store the picture.
If you want to save an image you found on the Internet from your mobile, run the full size, and then click on the button in the middle bottom of the browser. In the opened menu, click "Save image". The picture will appear in the folder "camera Roll" Photos.
Now on your iPhone go to "Settings" and select "Wallpapers and brightness". Here you can adjust the brightness of your screen, choose the new Wallpaper and also see what the picture is now on the splash screen. Click "Choose new Wallpaper". First you open the menu will be placed the standard of pictures you can put on the screen saver of your phone. Below you can see folders with images and photos.
Go to the folder where the desired picture. The preview opens where you can choose how it will look like this image on the lock screen or the home page. You can change the scale of the image and move it. On iOS 7 you can also select a point as the perspective through which the picture will move when you turn your phone sideways. If you are satisfied with the selected image, press "Set". Specify where the background should stand in this screensaver. You can close the settings menu - the picture will already be on the background of the main menu or the lock screen.