depends if you want use 3.2 or 3.3 or Minie.(3.2 -> 3.3 have new animation classes) Its generally similar, but you can solve things multiple way.
Sorry im not sure how IMU sensor work, but as i understand you generally need manipulate bones.
Myself i were manually only manipulating bone sizes, i didnt try manually move them.
see below and search keywords “armature” and “bone”, you generally would need use getSkeleton() and there was some methods for bone managing i assume:
You can also open SDK and “New Project -> JME -> JME Tests” and see there examples with bones.
You can also look at Minie project that is Physics based, and maybe you would want use physics based skeleton for your project.