Question: vrchat how to install avatars?
Answer: Install Unity 2017.4.28f1.
Install VRChat SDK.
Find an avatar you want to use.
Login into VRChat SDK inside Unity using your VRChat account (same as ingame)
Open .unitypackage file in Unity.
Select Unity Scene if provided in package.
Open Build Control Panel under VRChat SDK.
Click Build & Publish.