In fact it’s recommended to use monogame than xna because xna is abandoned by Microsoft ,
For the content project don’t worry I was exactly confuse like you , but in fact it’s straightforward
Don’t try to create a monogame content project into vs 2013, because it wouldn’t work, instead use the content pipeline , to do this -)
Search something called pipeline content.exe or something like this on you windows search bar , execute it ,
Before to explain you what to do I need to explain you how it work -)
In fact the pipeline.exe is a GUI ( graphical user interface ) for compiling your content to .xnb file that can be loaded from the content manager inside the code with a this.content.load TypeOfContent("contentWithoutExtension)
The content you compile can be various things like jpeg, png, sound , .fx file , font etc…
Then you jus have to grab the generated xnb to Content folder of your visual studio project by drag and drop , after , don’t forget to check on vs , if the file you paste has the right property : "copy if newer " that will simply copy your resource just to be used by your executable game.exe
So now , how pipeline gui work ?
Basically , create a new project inside , and you can right click on the tree at the left , and chose : add existing item , then you can chose your resource to be loaded like I said it can be various extension supported by monogame ,
Then when you are go , you click on build , then if everything is ok you will have generated xnb file ready to be used 
Tell me If you don’t understand something I will try my best to answer you because I was the same as you 3 weeks before !