Open the right-hand Insert panel.

Use the Image carousel option.

In the Insert images dialogue box use the Add image button (looks like a plus + and when you hold your mouse over it becomes a plus in a circle ⊕ ).

Choose to Upload images from your computer or Select images either By URL, by Search, from your Google Photos Albums or from Google Drive.

Once the images are added you can click and drag the images into the order you want, add alt text and add a Caption for each image.

 Use the Settings button (looks like a gear/cog at the top-right corner) to choose whether you want to 

• Show dots to demonstrate progress through the slideshow

• Show captions underneath each image

• Auto-start if you want the slider to start automatically

• Transition speed to progress from Very slow  to  Fast

Use the Insert button to add the image carousel to the page

Move the image carousel to the position you want it on the page and use the grab handles (blue dots) to enlarge or shrink the image carousel.