There's pretty extensive documentation on how to install/manage a wordpress site: http://wordpress.org/
hmmm i didnt really get it, it's like i managed to create another site, like www.mydomain.com/wordpressentry, but what im thinking of doing is to be able to edit www.mydomain.com like a blog.
Well the CMS that I use, you enter a very simple piece of code into the parts that you want to edit, and then viola, you go to the CMS site and can click where you want to edit, super easyt. Do you know any coding yourself? Id be willing to help you get started with CMS.