For a wall-to-wall print, you will need to split the selected image down the middle in Photoshop. Instructions can be found here:
First mount the cross profile printhead on the left side and print half of the image. Then mount the print head with the cross profile extension on the right side and position the print head exactly at the start point using the start point determiner.
We recommend that you first print the transition area of the 2nd image on a transparent film so that you can see whether you have hit the starting point and thus the transition of the image perfectly.