header menu help.

the theme I am now trying to work with doesnt have a header menu for pages. I added the following code to the header <?php wp_list_pages('title_li=&depth=1'); ?> which called the pages menu to be in the header.
The issue at hand is that the pages are listed on top of each other instead of side by side. I have tried about a dozen different options to try and solve this and can never get them to line up side by side instead of one on top of the other.

Does anyone know how I could fix this? Thank you.