How can animate extra limbs for humanoid rig?

I am animating a creature that is upper half humanoid, lower half octopus
(similar to Ursula from the little mermaid)

I need the rig to be humanoid in order to properly animate the upper body for VR, but that makes animating the lower half of the body a problem because there’s 8 tentacles and the humanoid rig only maps 2 legs, and the animator properties in the animation tab seems to only specify human body parts.

How can I animate additional limbs? (keep in mind I am a novice and therefor know nothing)