If you need to enlarge a picture in PowerPoint you can use the small circles when selecting a picture or change the size in the Format Picture dialog.
Resizing a picture in powerpoint is easy, you can just enlarge the picture by dragging the corner of the picture in powerpoint which will allow you to resize the picture without losing the proportions. However, another way to enlarge a picture in powerpoint is by entering the Format Picture box and change the Height and Width values.
Related: How to crop and compress a picture in Powerpoint 2010
You can also change the size of the picture to enlarge a picture by changing the Scale values by a desired percentage. If you want to keep the aspect ration then you should make sure to check Lock aspect ratio and use the relative to original picture size. Notice that unless you optimize the images in powerpoint or compress the images losing quality, you can reset at any time to the original size.
For this example we have used the free soccer photo for powerpoint that you can download for free from this same website.