Now that the site is installed and configured you can take care of choosing a theme and configuring the menus. (See Part 1)
There are many free themes available, as well as themes that come as a price. Finally, there is the possibility of hiring a professional WordPress Theme Designer to customize your site.
To find themes you can navigate to Appearances and then on the top “Install Themes” and then start searching for themes.If you download or purchase a theme from another site, you also have to go to Appearances > Install Themes, and then choose on the top “Upload“
A selection of themes can be found at smashing magazine: http://wp.smashingmagazine.com/2008/01/08/100-excellent-free-high-quality-wordpress-themes/
After you have selected and installed your theme you usually define a menu for your site. In most cases, you would want the user to be able to browse categories. However, you also can let the site navigate to Pages or custom URLs.
To allow the user to browse categories you first have to define categories, this is found under Posts > Categories. Whenever you create a new Post you should set a Category, if not it will be stored in the Category “Uncategorized“.
After you have set up the categories you can add them to your Menu. Important: You can set up multiple Menus, however, one menu is always set to the “Primary Navigation”.
Watch out that you always use the “Save Menu” button to save any changes.
Depending on your theme, it supports Widgets (small feature extensions). To add Widgets to your site, drag a widget from available Widgets and drop it where you want it (e.g. The Main Sidebar)
After you have dragged it you can configure it and how it looks.
Additional Widgets are available when installing Plugins see Part 3