You'll start here:
http://foundation.zurb.com/docs/index.php
Click on "The Grid" link on that page. This is part of what we learn from it:
The grid is always 12 columns wide. if you want three columns on your site, evenly spaced, then you would start with the <div class="row"></div> and put your "four columns" divs inside that (because 12 divided by 3 = 4, so, "four columns"):
Code:
<div class="row">
<div class="four columns">
One of your columns
</div>
<div class="four columns">
Your middle column
</div>
<div class="four columns">
Your third evenly space column
</div>
</div>