Hi Cate,
In customizr, you can easily make a colunm content in your pages or posts.
You will need to copy-paste some HTML code in your text editor.
1) In edit screen of a page/post, click on the text button (top right of the WYSIWYG text editor) : you can put HTML code here.
2) Customizr is built on a responsive 12 columns grid. If you want a 2/3 – 1/3 column layout, use the following code :
<div class="row-fluid">
<div class="span8">CONTENT COLUMN 1</div>
<div class="span4">CONTENT COLUMN 2</div>
</div>
Ohter example : for a 1/2 – 1/2 column layout, use this code
<div class="row-fluid">
<div class="span6">CONTENT COLUMN 1</div>
<div class="span6">CONTENT COLUMN 2</div>
</div>
If you want even more informations about this grid system, all documentation is provided here : https://twitter.github.io/bootstrap/scaffolding.html#gridSystem
Hope this helps and thanks for using Customizr!