TL;DR: Yes, but don't. Ugliness alert.
It is indeed a set of bindings directly onto the win32 API, which means you can use it to make a UI, but you essentially have to write like a C programmer who doesn't have a toolkit.
It's not pretty, and I'd like to strongly recommend you use a toolkit like GTK or WX, or better still a Functional Reactional Programming library like reactive banana. Those libraries will give you much more idiomatic and eassy-to-understand Haskell code, and portability comes for free.
Occasionally some library you use doesn't feature something you need, whereupon you might want to delve into the windows API.
If you're determined to use this, you need a good Win32 API tutorial to learn from, together with a good reference whilst actually coding. There are loads out there if you google, and plenty of books, but none of them fit into a stackoverflow answer. Whilst I don't know of any Win32 API tutorials written in Haskell, using the bindings provided in Graphics.Win32 means all the function names match up with those in the online documentation, so you should be able to translate.