1. Unzip fbxanimation.zip in hard disk and select it in addon preferences:Mixamo Animation Folder, and then press save.

2. Import Character button : Importing Mixamo Character inside the addon models directory into Blender

3. Combine Animation button : Combining multiple Mixamo Animations With NLA with accurate position transition in between mixamo animations 

4. Bake: Bake multiple NLA strips into one action and then export into one fbx Mixamo animation