We can get started by going to the http://www.mixamo.com/ website (there is a plugin that is integrated into the latest versions of Unity as well) and browsing through their library of animations:

Since we want to ensure that the animation will work properly with our character we can upload our character to Mixamo and see the animation being played on our character:

We have the opportunity to tweak any of the bones in our character to fit those that Mixamo has defined in their default skeleton. This will help ensure that our animation plays properly. In most cases Mixamo will map to the right bones by itself, but if you need to help it out because of some special mapping that you've done – all the tools are there:

Once mapped, we can reference this uploaded character as we browse through the catalog of animations in the Mixamo library when we create our own custom animations using the service. Now that our model is here we can look at exactly how the animation will perform, as Mixamo has an integrated Unity player on the website where we can preview and customize the animation as necessary.

We can adjust the sliders to customize our character motions in real time and get them precisely the way we want them. Once we've done that we can download our animation in the appropriate Unity animation format.

If we already have an animation that we want to import into Unity, we can use this same approach to import those animations as well. Unity supports two approaches for importing this content into our game: animation splitting and multiple animation files.