You have to be registered as a user - there's a link for doing that in the second paragraph of the blurb about OlyBlog.net that's in the gray right sidebar on the right of each page.
Then you can log in with your new user id and password. You click on the link labeled "create content" in the left menu, and get a page that offers you several choices about which kind of post you want to create. If you want it to be on the home page, it should be a story or an event. (The titles of event posts appear on the calendar and have to have a date and time.) Your blog posts will appear one after another in your section of the blog, and they will show up in the list of recent posts, but a blog post won't be displayed on the front page (unless you use the pull-down "Publishing options" menu at the very end of the edit page and check the "Promoted to front page" box). Please don't post new stuff by adding comments to this page about how to use the website - unless you want to comment about what this page says.
When you click on the post you want to create, you should get a page where you can type your post - you put the title in the Title field, and what you want to say in the Body field, and then click the Submit button at the bottom of the page. If you need to change something, you can click the Edit button, make your changes, and then click Submit again - as many times as you like, provided no one has commented on your post yet. Once that happens, it's permanent, and if you want to revise it further, you just have to make another comment on your post yourself...