Here is what it currently looks like. Do I need to attach the character to the ground with code or is it something I need to do set in Blender?
Hi again TT.
In our previously-used model/playground… https://www.babylonjs-playground.com/#1CMD3G#105…
there ARE already animations on-board. See JS console… and lines 40-50 where I examine the model’s skeleton/armature and bones.
MOST of the bones have animation installed… but I do not know how to start it, or if it will work properly. Maybe best to get animations working perfectly in Blender, and then re-export WITH a root mesh (a master parent), which might have an .animations array, which might have something we can start().
Generally speaking, we have had good luck with Blender animations… exported to .babylon files. Blender would be a great place to SEE the animations on your mixamo model… make sure they look good… then export. Lots of learning ahead, for you. Good adventure.
Maybe others will have ideas about the animations installed on your model. I “played” one animation on one bone, using the playground’s inspector feature. It looked pretty ugly. 
Player reached thru the floor and up again, and poked his arm thru his head. 