When you log into blogger, it'll direct you to the "My Dashboard" page, where you'll see the blogs you own listed like this:
Click on that plus sign and you'll get taken to the post-creation page:
Just type in your sakubun and give it a title and hit PUBLISH POST. "Save to Draft" will save your post but only you will be able to read it. If you think you posted and it shows up in your dashboard's post area, but not on the blog itself, you probably hit save to draft instead of publish post and you'll need to edit the post.