How to use a picture from the internet as a wallpaper?

Everytime i click save image on my iphone 5 it saves the picture but it is to large for the screen. WHat can i do to fix that? It does not automatically adjust it like it used to

I-phone have setting to change sceen resolution. But if not then download apps from the store for same purpose.

Pinch-Zoom/shrink image to fit your screen then
screen capture(print screen) and later you can use it as wallpaper and will fit perfect to your screen.

The picture maybe not right, you can search for some apps to adjust the size.