I installed Xamarin Studio for Windows 5.5 but I don't see the F# templates nor I can display the F# interactive. I could create F# projects without problems in Xamarin Studio for Mac so I'm not sure what's the problem. Also, please note that I have already installed the F# compiler tools as instructed in this guide: http://fsharp.org/use/windows/
FIrst thing to check - make sure that the F# Addin is installed (it should be) and enabled (Under Tools > Addin Manager, then Language Bindings). If it isn't enabled, you won't get the projects in the list. Then after enabling it, you might need to restart. Hopefully that should resolve your issue.