can't find image texture node in node editor As you can see screen capture I took, I can't find any image texture in the add menu.
All the videos I saw, there was an image texture node in Add > Texture > Image Texture, but I even can't find the first depth. 

version is 2.78
Based on the node I see, you are in Blender Internal Render. If you switch to Cycles and add a new material, you will find the Add > Texture > Image Texture.