The video below shows the process of update a page summary (click the button on the bottom right of the video to expand the view). You can also follow the screen shots and steps below this.
3) Find the page which contains the image you would like to modify
4) Find the image on the page you would like to modify.
5) Right click on the image and click Properties.
6) Then at the bottom fill in the Vertical Spacing section if you want spacing at the top and bottom of the image, or Horizontal Spacing if you want spacing on the left and right (or both if you want spacing all around). Please note: If you add horizontal spacing to a large image (490 pixels) this will cause formatting issues in some Internet browsers. Please do not add horizontal spacing to large images.
You should add the amount, in pixels, of spacing you would like. Between 8-10 is a good amount to choose. Click OK.