There are various ways you can do this.
The recommended basic way to set up a slideshow is as follows.
- Prepare the slides using PowerPoint or an alternative. Allow some space around the edges in case you want to trim the images. The default proportions of a slide are 3:2 e.g 600px x 400px or (better) 1200px x 800px. You can use a custom size on PowerPoint to match this if you wish.
- Save each slide as an image (png is preferred) and load them as media files in WordPress. Using Save as in PowerPoint is probably the simplest way.
- Create one page for each slide in the sequence. It may help to use a numerical slide name suffix for identification and sequencing. Make sure you select the custom template called “Slide page”. It may help to make each slide page a child of the first slide.
- On each page add one slide as the Featured Image.
- Go back through the slides and set the page sequencing (see separate document).
- Add the first slide in the sequence to the menu.