This will only be a step-by-step to add the plugin to BlogEngine.

1. Download SyntaxHighlighter

2. Download plugin

3. Copy SyntaxHighlighter to BlogEngine's root folder

4. Copy plugin to editors plugin folder

5. Add the following line to the top of your selected theme's masterpage.

<link rel="stylesheet" href="~/SyntaxHighlighter/styles/SyntaxHighlighter.css" />

6. Add the following section to the bottom of your selected theme's masterpage.

<script language="javascript" src="/SyntaxHighlighter/scripts/shCore.js"></script>
<script language="javascript" src="/SyntaxHighlighter/scripts/shBrushCSharp.js"></script>
<script language="javascript" src="/SyntaxHighlighter/scripts/shBrushXml.js"></script>
<script language="javascript" src="/SyntaxHighlighter/scripts/shBrushCss.js"></script>
<script language="javascript" src="/SyntaxHighlighter/scripts/shBrushSql.js"></script>
<script language="javascript" src="/SyntaxHighlighter/scripts/shBrushVb.js"></script>
<script language="javascript" src="/SyntaxHighlighter/scripts/shBrushJScript.js"></script>

<script language="javascript">
    window.onload = function() {
        dp.SyntaxHighlighter.ClipboardSwf = 'SyntaxHighlighter/flash/clipboard.swf';
        //this section is important to allow for the correct formatting of BR tags
        dp.SyntaxHighlighter.BloggerMode();

        dp.SyntaxHighlighter.HighlightAll('code');
    }
</script>

7. In the admin folder, locate the tinyMCE.ascx file and change the following

<script type="text/javascript">
    tinyMCE.init({
        // General options
        mode: "exact",
        elements : "<%=txtContent.ClientID %>",
        theme: "advanced",
        plugins: "inlinepopups,fullscreen,contextmenu,emotions,table,iespell,advlink,codesyntax",
        convert_urls: false,
        
      // Theme options
        theme_advanced_buttons1: "fullscreen,code,|,cut,copy,paste,|,undo,redo,|,bold,italic,underline,strikethrough,|,justifyleft,justifycenter,justifyright,justifyfull,|,bullist,numlist,outdent,indent,|,iespell,link,unlink,sub,sup,removeformat,cleanup,charmap,emotions,|,formatselect,fontselect,fontsizeselect,|,codeformat",
        theme_advanced_buttons2: "",
        theme_advanced_toolbar_location: "top",
        theme_advanced_toolbar_align: "left",
        theme_advanced_statusbar_location: "bottom",
        theme_advanced_resizing: true,
        extended_valid_elements: "pre[name|class]",
        tab_focus : ":prev,:next"
    });
</script>

8. Now you are done.

Your Add Entry editor should now contain a dropdown like the one below

It works the same as formatting text inside the editor, just select the text to change and then the format at has to comply to.