There are two different ways in which you could include a powerpoint presentation in your ePoster/Stack:
1. As a File (PowerPoint)
The first would be to add a File tile from the Tile Library and then add the powerpoint file in the Add File box that appears to the right. If you watch video 3 (Creating an Poster from a template) between time 10:20 and 11:05 then you will see how we use the File tile to add a PDF file to an ePoster. To add a powerpoint file you would follow the same steps, but upload your powerpoint file instead. Learning Toolbox will automatically convert your powerpoint presentation into a PDF file so that it can be viewed inside the PDF viewer within the Learning Toolbox app.
2. As Online Content (Using Slideshare)
Another approach you could use is to first upload your powerpoint to slideshare https://www.slideshare.net/ This will then create a slideshare version of your powerpoint that is viewable online (and within the Learning Toolbox app). Within Learning Toolbox you can then add an Online Content tile to your ePoster and add in the url link to your slideshare presentation. Doing it this way will mean that people can view your presentation within Learning Toolbox itself, they will not need to have any other special software installed. If you watch video 3 (Creating an ePoster from a template) between time 9:48 and 10:20 then you will see how we use the Online Content tile to add a Youtube video. To add a slideshare presentation you would follow the same steps, but paste in the url of your slideshare presentation (instead of the url to a youtube video).