I assume that your slideshow is running images and the images are too large. You can reduce the size
of the images in an app like Photoshop.
Open the images and reduce their dots per inch (dpi) to 72, then change their size to the minimum needed
by the slider. If the slider wants images that are sized 1,000 x 400 pixels then make them that size.
Finally when saving your images, use the JPG file format and set the quality (compression) to 7.
Doing those 3 things will reduce the size of your image so they’re no longer huge.