For each function you want to call you need to add it to a DECLARE (CUSTOMTYPE|DYNAMIC) LIBRARY block. You then link with vfw32 directly, no need for a header file.
I'm not savvy enough on details of Windows linking to know whether you should be linking with the vfw32.a static library that comes with mingw or if there's a system-wide dll to use.
However it may all be a moot point because from a casual glance at the linked article it appears the whole shebang is partially driven by handling window events, which you can't really do in QB64.