After opening or creating a project you can continue or start on your course.
Every project that you create will have different steps in order for the player to be able to finish the course.
Those steps we call bubbles.
To add a bubble to your project you click on the 'Add Bubble' button.
Every bubble is created around an asset.
These assets are available in the 'File Explorer'.
Select the folder the image is in (or upload a new one by dropping it in the marked box):
After choosing the image, you should now see it in your Creator course: