Garyfrogeye is using the Website Wizard. Wizard creations should not be edited by any editor outside of the Wizard, which leaves out using the Visual Editor. However, changing the width and height of an image could be done within the Wizard using the Code Editor mode, when you are in a content editor.
However, that isn't a recommended method. Using the image attributes to change the size, forces the visitors browser to resize the image. You need to be careful to change the width and height by the same percentages. Otherwise the image will look distorted. Browsers also do a very poor job of resizing. If your going to resize a image, use something like IrfanView, which is a good free graphic editor with an excellent resampler. This gives you a much cleaner resized image. Using the image attributes to change the size also wastes bandwidth.
The entire image much be downloaded by the visitors browser before the image can be sized down. It would be better if the image was already the size you require, before you add it to a page.
The small image you talking about, is usually referred to as a "thumbnail". It's common to have "thumbnail" images linked to larger images. The graphic editor I linked above has a built in thumbnail generator. It is capable of generating an entire HTML page of thumbnail's linked to their larger images. It works rather well.
You might also want to look at Dynamic Drive - Image Effects. These are Javascripts that can be used to get lots of different effects. Note, because you are using the Website Wizard, man of them will not be easily used. The Wizard has a unique ability to disable Javascript. I can make any of them work in the Wizard, but if you don't understand Javascript, it is difficult.
