Apple Motion 2 Tutorials - Manual (Page 182)

182 Tutorial 4 Working With Particles
Importing a Particle Cell Source
The Library contains a Sun particle preset, which needs no modification for this project.
Simply add the Sun particle preset to the project, and you are finished.
To add the sun particle preset:
1 In the Library, select the Particle Emitters category, then select the Nature subcategory.
2 Drag the Sun particle preset to the upper-left corner of the Canvas.
The Sun particle preset appears where you release the mouse button.