I have to design a website, but I'm not sure where to start

To change look & feel you need to edit css associated with the theme.
To add/edit navigation items and dropdown you will have to add/ edit navigation from the wordpress admin panel.

 

One thing people starting with WP have problems with is understanding the different between blog posts and 'pages'
The basic idea is that blog posts are a bit like diary entries - you add a new page every day or so and it pops up on top.
Pages are more like traditional websites - you set them up and they stay there for ever without changing.
Sounds like you might want to just use pages? You don't have to create any blog posts at all - if you don't want them
You can group pages, by choosing top level ones then when you write other pages, selecting one of the top level ones as 'parents'
If you want to just use pages on your site go to dashboard, settings, reading - and select a static page (that will open when anybody first visits your site)

 

Check out this Link

http://wocservices.com/2011/01/11-must-have-online-resources-to-be-a-better-web-developer/

 

Website design can be so fun and yet so frustrating. Edit the theme colors and fonts in the css files from the edit theme section of wordpress. I have tried Joomla, Drupal and Wordpress and am sticking with WP when building a site for somebody else. It is just so much easier for THEM to maintain.