To the best of my knowledge, there are two ways to determine force sensitivity.
1) A force user tests your connection to the force
2) Use a Force Detector item on yourself. Bear in mind these are only obtainable from bandit (NPC drops) or purchasing them from the market.
It should work regardless of ownership, particularly as you can use it on others and not only on yourself. But given that things don't necessarily work as they should here, please let us know if you observe different behaviour.
It needs to be equipped to a utility slot in order for you to see the Use Item option on your equipment page.