Previewing your graphics and ad sets can be done following the steps below.
Click the Matches button in the left hand side dashboard..
Hit the 3 ellipsis next to the corresponding match that you wish to preview graphics and ads for and then select Settings under the Overlay section.
Select the template that you would like to preview and also the relevant ad set. In the below example, the Intro graphic is selected with a Large ad displayed.
In the next example, the MatchID graphic is selected with a Long ad displayed.
In order to use customisable ad sets, the user MUST be using a Graphics + Brands time of their productions.