I know there's a quicker way to get there, but I just click on someone else's blog on the right hand side of the screen.
When I get there on the left hand side, under "Options" there's a link that says "Post to your blog" or something like that.
When you click on it, you'll get a screen that looks just like it would if you're going to start a new thread.
If you're a paying member, it doesn't cost extra.