Hi.
you can use some box colliders for the chair and 1 box collider as trigger (bigger than chair) that will be set as trigger.
Then when player interact, you probably want a target point where you let the player move to and rotate (so his back is towards chair) and do a sit animation.
There are some character controllers on the asset store that can do all out of the box, but many do not have direct playmaker support. (you can still use Get/Set Properties and invoke to communicate with it, but its a bit more complex)
