Commercial themes require support from the vendor per forum rules
That said, review this:
To discover what CSS is output by your theme, use a web inspection tool such as Firebug: http://getfirebug.com/ , Chrome Inspect Element: https://developers.google.com/chrome-developer-tools/ or Internet Explorer 9+ F12 Dev. Tools: http://msdn.microsoft.com/en-us/library/dd565627(v=vs.85).aspx#csstool
There are others.
When editing CSS, use a Child Theme
http://codex.wordpress.org/Child_Themes
Custom CSS Plugin, or Theme provided custom CSS option.
Edits to parent themes are lost on theme update.
Learn CSS: http://www.w3schools.com/css/
Find out more at:
http://codex.wordpress.org/
It looks like you could possibly make this wider:
#nav-left {
display: inline;
float: left;
width: 450px;
}
But if that doesn’t work, you should ask WooThemes for help:
http://www.woothemes.com/products/gazette/
As we don’t support commercial themes here – partly because we don’t have access to them.
That was actually the first thing I tried – turns out it did work, I just needed to clear the cache! Thanks so much for your quick response.