How do I import a PNG sprite sheet and run its animations while the stage is playing?

I need to keep related animations in a single PNG sprite sheet so that they are loaded efficiently at run time in my game’s engine, and also so they are easier to work with.

Adobe Edge Animate makes this easy with its Import Spritesheet... function. How do I do this with Toon Boom Harmony Stage? Do I need a plug-in or something?