Spacing Custom Menu Widget in Header

First of all, I love the Pinboard theme so thanks for making it!

I have created a simple sight for a friend. We wanted to put the menu into the header so I did using the Custom Menu. I then made it horizontal by putting:

.menu-item{
display:inline;
}

into the custom css under theme options and layout.

The menu items, however, are all crammed together. My question is how do I change the spacing on the menu items. The sight is here:

http://www.lynnliverton.com/wordpress/

You can see that About Contemporary Monuments … etc are too close together. How can I change the spacing? Thanks!