It is important to note that the competition logo is not used in all graphic themes, in some themes only the name of the competition is used. You can add the relevant competition logo that will display on your templates when you first create a competition.
When the competition logo is used, it will usually be seen in full-screen graphics like the Intro graphic and match ID graphic, however, you should check each graphic theme for the exact placement and if the competition logo or just the competition name is being used.
See the image below for an example of how the competition logo is used in one of the graphics in the Rigel theme.