Create new slider from scratch.
Click NEW SLIDER from Dashboard.
Creating new slider
Click ADD NEW SLIDE to add image or video files to your new slider.
WordPress media library window will open, where you can upload files, or select them (if they are already uploaded in media library).
Supported files are: jpg, jpeg, png, mp4, webm, ogg.
Upload files to Media library
Select files from Media library
Once you're done with choosing your images/videos from media library, click Select and your slides will appear under Slides tab in Dashboard.
Added slides to slider
Done, you have added slides to Transition Slider.
At this point, you can Save your slider and it's ready for usage via Shortcode. See more in Editing slider -> Publish section.
Additionally, you can always edit slider settings, add more slides, or edit each slide individually by adding layer elements etc.