Hi JWS
If you’re using the default MODx Template, you won’t be able to directly edit the right column of the site. Just because it isn’t setup for this purpose. If you have a look at the Template code you’ll find the following:
<div id="right-inner">
<h1 style="text-indent: -5000px;padding: 0px; margin:0px; font-size: 1px;">[(site_name)]</h1>
<div id="sidebar">
<h2>News:</h2>
[[Ditto? &startID=`2` &summarize=`2` &total=`20` &commentschunk=`Comments` &tpl=`nl_sidebar` &showarch=`0` &truncLen=`100` &truncSplit=`0`]]
<div id="recentdocsctnr">
<h2>Most Recent:</h2>
<a name="recentdocs"></a>[[ListIndexer?LIn_root=0]] </div>
<h2>Login:</h2>
<div id="sidebarlogin">[!WebLogin? &tpl=`FormLogin` &loginhomeid=`[(site_start)]`!]</div>
<h2>Meta:</h2>
<p><a href="http://validator.w3.org/check/referer" title="This page validates as XHTML 1.0 Transitional">Valid <abbr title="eXtensible HyperText Markup Language">XHTML</abbr></a></p>
<p><a href="http://jigsaw.w3.org/css-validator/check/referer" title="This page uses valid Cascading Stylesheets" rel="external">Valid <abbr title="W3C Cascading Stylesheets">css</abbr></a></p>
<p><a href="http://modxcms.com" title="Ajax CMS and PHP Application Framework">MODx</a></p>
</div>
<!-- close #sidebar -->
</div>
There you have a Ditto Snippet call, that outputs the latest news, and some more Snippet calls to show the latest Documents together with a Login Form. The links to the validators are hard-coded.
You can obviously change the contents of the "News" section by editing the "Blog" subtree of the site. That’s where Ditto looks for the documents in this case.
You could however completely replace that content in the right column by something you like. For example: Create a Template Variable with the name "MyContent" and choose "RichText" as input type. Assign this template variable to the template you’d like to use it in. Example: Assign it to the MODxHost template by klicking the correspondent checkbox.
Now you have to alter the MODxHost Template. As an example, you could replace the whole code-block posted above with the following code:
<div id="right-inner">
<h1 style="text-indent: -5000px;padding: 0px; margin:0px; font-size: 1px;">[(site_name)]</h1>
<div id="sidebar">
[*MyContent*]
</div>
<!-- close #sidebar -->
</div>
Now you replaced the whole content of the right column with some user-definable (Template-Variable) content. If you edit your "Home" Document you should now see another Richtext editor for your Right column.. put something there and see if it works.
The possibilities are basically endless

Good luck