How to make an image a full page?

Zoom out so you have a lot of grey space around the page and click on the image. Hold down and move the top left of the image to the top left of the page. 

Next, place the cursor over the bottom right blue square, hold and pull out the image to cover the whole page. 

Next, double-click the image so a black box also appears. The black box is the picture frame that the image goes behind. 

Using the arrows on your keyboard, you can position the image. View the thumbnail as this shows you how it will appear on the page.