Start by going back to their website
Accord.NET Machine Learning Framework[
^] and follow the "read the manual" link.
That's a little sparse, but it gives you links to a "getting started guide" and a sample application.
Start there, and if that isn't enough the full documentation is available on their site under the "Consult the API" link. You will need to read quite a bit of that in conjunction with the other guide and the sample app to get the best use out of the package, I suspect.