I'm getting "The type or namespace name 'Forms' does not exist in the namespace 'System.Windows' (are you missing an assembly reference?)" from "using System.Windows.Forms;". Various people on the internet say to add it through a "References" tab in Solution explorer, but for me it's not present:

How do I get the references tab to appear, or how do I otherwise get "using System.Windows.Forms" to work?