Step Motion should be easy to use, but feel free to read the documentation, or watch the video below.

Documentation

We'll go through all the functions Step Motion has. Let's first make sure that we have setup Step Motion properly. After installing the addon (StepMotion.py) you could either open the "StepMotion.blend" file or append the "Step Motion Preview" object to another Blender file. Step Motion makes use of the Step Motion Addon, Step Motion Preview and Step Motion Shader, here's what they do.

Step Motion Addon

Create Step Motion
The first time you open the Step Motion panel, it'll only say "Create Step Motion", pressing this will open the other menus, create a Collection called 'Step Motion' and one called 'Frames' and create your first frame; a smoothed Sphere.

Create

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New Frame (ctrl + shift + N)
Creates a new frame, containing a smoothed Sphere.

Duplicate Frame (ctrl + shift + D)
Creates a duplicate of the current selected frame.

Add Object
When an Object outside of the Frames collection is selected, and Add Object pressed, it'll be moved to the Frames collection and renamed to Frame

Set Position
Set the position of the selected Frames to the World Origin

Visibility

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Mode
Changes every Frame in the Frames collection to Object or Sculpt mode

Frame (ctrl + MouseWheel / LeftMouseButton + Drag)
Displays current Active Frame number

< > (ctrl + ArrowKey Left/Right)
Flick through Frames 

Onion Skinning
Turn Onion Skinning on/off (only works when animation is paused)

Frame Visibility
Turn non active Frames Visibility on/off (only works when animation is paused)

Finish

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Finish Step Motion
Renames Frames collection to 'Animation', deletes Step Motion Collection, and resets Step Motion Addon.

Export

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Start / End
Start and end Frame of exported .abc

Export .abc
Exports Alymbic to current Blender file location (Object with Step Motion Preview Geometry Node has to be selected and 'Realize Instances' turned on)

Step Motion Preview

Frames Collection
The collection that will be played as an animation

FPS
Speed of the animation

Use Material / Material
When activated, uses the Material selected below. When deactivated, use the individual frames Materials

Loop
Loop the animation, deactivating starts 'Key Frames'

Key Frames
Use to keyframe frames

Realize Instances
By default deactivated, active before exporting .abc