I do a search in google for information on how to create a clipping mask with a shape on a photo to eliminate the background but the results it gives me references options I cannot find in my Google Sketchup menus. Anyone know how to to do this or why I can't find the option? Here's what they have listed:

You can mask out a portion of a model, image, or text by creating a clipping mask or shape that represents the portion of the mode or image you want to see in your presentation. To create a clipping mask:

Place a shape over an image or model.

Select both the shape and the image or model.
Context-click. The context menu is displayed.
Select the Create Clip Mask menu item. A clipping mask is created