The Logo Tool is located in the Adornments Tab and is used to place an image to your map that is in a fixed position, regardless of panning, and will be carried over to your Print map.
The Logo button will open the Logo window and allow you to browse your computer for a file that you want displayed on your map. Once an image is selected, the Preview panel will display the image you have selected.
Location - Sets where the image will appear in the map
Left and Top Offset - Offsets the Location by a number of pixels. This can be a positive or negative number
Size - Sets the image to either be sized automatically or a fixed size based on the Width and Height on the right hand side