Storyline's caption shapes give you a quick and easy way to create labels, speech bubbles, and thought clouds.  Here's how to add a caption shape:

1. From any slide or slide master, click the Insert tab.
2. From the Caption menu, select the caption type you'd like to add.
3. Click and drag on your slide canvas to add the caption to your slide, and, if the caption will include text, you can immediately begin typing—there's no need to insert a separate text box over the caption, since the caption shape can hold text.
4. The initial fill color, line color, text color, and font of your caption are determined by the design theme you're using for your course. You can change the look of your caption, though, by selecting the object and using the tools on the Format tab to apply any formatting effects that you like, or click the Home tab to adjust its text properties. You can also right-click the caption and choose Format Shape or Size and Position, and use the tools provided there.
Note: If you apply some formatting to a caption and then want that same formatting to be used on future captions you add to the current course, you can right-click the caption and choose Set As Default Shape.
5. If the caption type you chose includes a pointer, you can make it point anywhere on your slide. Just click and drag the yellow handle at the end of the pointer.