A fallback image is just a PNG or a JPG that can be uploaded to the campaign in the given DSP.
You are exporting it as you are exporting to any other network.
However, depending on how many campaigns or creative sets you need fallback images for there is a slightly different way of choosing what to export:
Fallbacks for more than one Creative Set or a Campaign
Choose Campaign or Creative Sets:
Campaign: If you want to export fallbacks for all creatives set within one Campaign you can click on the three dots right next to the name of the campaign name and click on 'Select all Creatives set'
Creative Sets: If you would like to mark specific creative sets you mark the creative set by clicking on them (the blue line around them shows that they are marked).
Now click on 'Export' at the top.
Now jump to point no. 3 below 👇
Fallbacks for a specific Creative Set
Click on the three dots for the specific Creative Set
Click on 'Export'
Now the pop-up window is showing all the creatives to the left and the export options to the right
Export options: Choose PNG
Below the visual of the creative, you have a timeline.
You can either drag and drop the pin to which frame you would like or click 'Play' and 'Pause'
When you have chosen the frame you would like to export click on the timer to the right so you can see that the time is entered.
Click on 'Export'
Happy exporting 👏