WordPress and Yahoo HELP!

I am using wordpress via yahoo…I uploaded the program and put it on my website. Now for the dumb question, how do I change the blog? Do I have to re-upload the program and just keep redesigning the blog? I don’t really want to redesign, I’m just trying to post new questions and stuff, but I don’t know how to get it onto my site. I am totally new and obviously clueless about all this stuff!