How to blend between poses

I’m trying to implement the stuff in this video, Animation Bootcamp: An Indie Approach to Procedural Animation - YouTube its the GDC talk with David Rosen on how he did the animation for Overgrowth. Basically,
. He has two running frames(pass and reach pose).
. Based on the distance travelled, switch between them.
. Blend between the two frames.

I’m guessing I want to use pose assets and just blend between the two, but I’ve had a hard time getting this to work.

New to the engine, so lacking direction, any help is appreciated.

Bit confused as to word use.

Are you referring to Additive animations?