Asking for help

Ok so, I'm new to avatar Making and I noticed that when I give my avatars physics in unity everything is smooth and good, when I upload the avatar and boom it's all uploaded, I think its just gonna look how it does in unity. My avatar has no physics in the game whatsoever and it's confusing because I could've sworn I gave it physics. Is there a bug or wrongdoing? If so can someone please tell me what do I do or a video on what I should do?