Do you knwo C# as it is?
I only ask because you don't need someone teaching you how to do it, Microsoft already documented it.
c# made it really easy to automate websites (I prefer that to bot, sounds less nasty).
What your going to need to learn is the XML parsing. The hardest part is reading the web page your going to be automating. Its a matter of research though. All you REALLY need to do is identify the input boxes. I mean, that are their IDs. Then, in your app, copy your string to the box then generate a mouseclickevent on the button that submits the information.
So you only need an imput box for the login info and then you load what your posting from either files or scraping.
Instead of searching for that I think you'd better spend your time just digging in the MSDN library because I know there are about 100 examples of how to do this, with source code.
Sorry I didn't post a code tutorial but botting in c# is one of those things you gotta teach yourself to maintain it. Good luck and if I can help just let me know.