The video is a series is of 4 videos, posting the last part since this series that I'm posting is on how tweaking existing models and not doing them from scratch. Some 3D models already come with a bone structure which allow to do animations, found in previous tutorials. You can skip those first 3 steps if you are following this logic.
The Free 3D models most of the time are not animated, since the artist does not know what the 3D model is going use to. It can be a wizard and cast spells, which is 1 type of animation or a warrior and only attack with swords a different type of animation. Some of them come with simple animations : idle, walk, run, simple swing, etc...
If you need you can search for step one of the animation, which is the rigging part, but the models you download from free materials most of them, or some, come with a bone structure also called rigged. Since they come with that part done, this step is enough to follow on, how tweak free models.
The tutorial explain how to follow a animation plan, this make the animations more realistic, if you just doing it by your self with out a animation frame plan. Consumes less time since things are already set up to do the animation.