How to animate a hand drawn 2D character?

I am making a 2D side scroller, with a cartoon style artsyle. I have an artist who has made a 2D representation of my hand drawn character. How do I animate him for walking, running, or even in action? I know I can use blender but how is that possible? Do I have to draw each frame of my character for a specific task? I would like my character to walk smoothly and not look awkward like most 2D games.

Also I understand the scripting aspect, but all I need to know is the movement of the character.

Thank you, and please be clear and concise as I am a beginner to Unity.

See the Unity tutorial on 2d Character Controllers:

This shows how to load in frames into the animation editor.