How to make the video not widescreen?

I have an iphone and i'm trying to edit a video on imovie on my macbook but I'm confused on how to make it in standard or iphone screen.

The aspect ratio needs to be 4:3.So Normal Pal resolution is 720*576.

Every IPhone they have made is different. So need to know what one. The Iphone 5 for example is 640*1136 Wide thats almost but not quite 720. The Iphone 4 is 640*960 more of a square size.

This idea is not logical. The production company made the aspect ratio. It is not useful for you to change it. Widescreen movies play on iPhone fine. You will see black areas above and below if the aspect ratio is wider than the screen. This is normal. It is called "letterboxing". See the link below.

If you change a widescreen movie into a narrow aspect ratio, the people will look extremely tall and thin, and a round object such as a basketball will appear to be oblong, like a rugby ball on end.

When a widescreen movie was adjusted for broadcast several years ago, when many people still had old SD TVs, the effect used was called "pan and scan" (or worse, "center cut") and involved a device called a film scanner. The scanner operator chooses the part of the scene he wants to include. The scan process then crops off one or both sides of the scene. This preserves the shape of people and objects, but loses some part of the scene.

Nowadays, with 90% of folks using HD / widescreen TVs, the movies are broadcast with no change to how they were originally filmed. The TV will add the black above and below "Fiddler on the Roof" (Aspect Ratio 2.35 to 1 ) and on the sides of Chaplin's "Gold Rush" (Aspect Ratio 1.33 to 1). We wouldn't want everyone to look like bean poles in Fiddler or like pumpkins in Gold Rush, and we want to see the whole, wide scene with no pan and scan cropping off of the sides.