How do i use bones?,How do i see the bones?

I am in version 2018.4.20f1 and trying to fix the bones of my VRoid avatar that i imported into unity. When i uploaded the avatar into VRChat, the legs were weird (bending inward) so i wanted to figure out how to fix the bones. I do not want to update unity in case it ruins the avatar (which can only be imported and used in version 2018.4.20f1). I don't know how to see the bones of my avatar or how to use/manipulate them, so it would be really helpful to know how to do that in this version specifically, since all the advice i have been finding is from very old versions or the newer version, and exploring on my own isn't getting anywhere. This is my first time using unity and i'm not the best with tech, so i do not know much or anything about it and it would be really useful to have specific details or pictures if possible. please help, thanks,I have a vroid avatar i imported into unity for vrchat. The legs were acting weird, so i figured i should change the bones. I looked up a lot of videos and sites since i know almost nothing about how to use unity. I am using version 2018.4.20f1 and cant find the right information to find out how to see the bones of my avatar and fix them, so i was hoping asking a question here would give me an answer. I do not know how to see the bones or use them in this version.