How do I add spaces to my post?

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I have seen nice clean post, where people have line breaks in their posts. My post are always lumped together like one long paragraph, whether I add a break or not. I tried adding html, but got an error message and had to rewrite this post. So, that is not it. I know there is a separate message board language, is that what I use? I don't even want to attempt it now, for fear I will get another error message and have to rewrite this again. How do you add line breaks?