Watch this short video tutorial to get a feel for the SampleBoard...
Similar to using a clipping path in Photoshop, you can remove the background of an image using the Background Clipper tool in the Basic Edits menu within the editor. You will find the tool near the bottom of the Basic Edits menu.
If you have a complicated background with lots going on, it's best to use the Custom Background Clipper as you have more control. Simply click to draw the path of the image you want to keep and click Save.
If you have an image with a solid background color you wish to remove to create that "transparent" look, the Solid Background Removing Tool is the best option, as you can remove the background with one click.