Some digital signage displays are set up to allow users to edit the slides via Google Slides. You must have permissions to edit the slides and permission may be requested through the marketing department or your supervisor.
Once you have permission, to edit the slides you will need to log in to http://slides.google.com. After you have logged in, find the presentation that you are trying to edit and open it up.
Once inside the editor, you may add, remove, or adjust the slide order by editing the slide thumbnail on the left hand side. If you need to edit text on a background slide, you may do so using the editor on the right.
As of the time of this Solution publication, the timing of the slides was done by a script, not what the timing is set to inside the presentation.
For further knowledge, the Google Presentation is fed to the display via Risevision. There is no need to adjust anything inside Risevision once the display is set up.