You need to publish your weblog.
Most blogtools work in one of two modes, create all files in advance or create them on the fly. This is sometimes referred to as baking or frying. MT bakes the files.
With MT, your content is stored in database tables. You then use the MT admin interface to generate (bake) HTML and CSS files from the templates and the new content you have entered.
Other blog tools take the frying approach. When a URL is requested, the blog tool generates (fries) it on the fly if it doesn't already exist.
The advantage of baking is that the user experience is more consistent. The downside for the blog publisher is that publishing a large blog can take a very long time. For example, if you make a change to the template for individual entries, MT will need to regenerate nearly every page of your blog. Some webhosters have banned MT, because this can be a very CPU-intensive process that runs for several minutes.
The advantage of frying is that your changes take effect the next time a page is requested. The downside for readers of your blog is that this means page requests can sometimes be much slower than normal. This downside is somewhat offset by the fact that web spiders, like Googlebot, will take care of this for you if they are already indexing your website.