I'm refering to the "Class" called game.cs. It's in the picture as well. Essentially, your code is asking for an object called "Content", Content exists in the Game.cs class, which inside is usually named Game1.
This function for loading enemies needs to be inside the Game1 class, or the Content object needs to be exposed to the other class some how.
Ive now done this, I've moved the loading enemies into the Game class in the LoadContent() region however I'm getting the same thing :S
Also, what is the book you are using. They are having you repetitively load an image during game play. That's typically a bad idea, as it is faster to load it once in to a variable, and then reuse it as you need.