One thing that you should be aware of when you build your first ‘real’ F# application, is that in F# file order matters. F# requires files (and code within) to be in dependency order. This means that you have to rethink how to organize your code. Have a look at the following post on http://fsharpforfunandprofit.com/(great site btw for every F# developer out there):
http://fsharpforfunandprofit.com/posts/recipe-part3/
Luckily Visual Studio provides some context menu options that allow you to re-order the files inside your F# projects: