How could I get this Vim binding to work?

qnamebuf plugin description says:

<S-F4> opens an explorer from the current working directory showing all fi开发者_JAVA百科les which are not in a hidden directory (one that starts with '.')

I'm not very good with Vim, but I imagine S-F4 is a capital S followed by F4. However, when I press S, I find myself in insert mode, and pressing F4 after this, just adds an F4 in the window. What should I do to make the command work? I am running gVim under Windows.

The S stands for Shift. So try pressing Shift-F4.