The functionality I'm about to describe is highly dependent upon your current theme, however, most modern themes these days support header customizations, so learning a few things about this feature will surely come handy to you sooner than later.
If you're starting your WordPress adventure with the default theme, Twenty Thirteen, in the Appearance section, you can see one link labeled Header. This is exactly where you can adjust the design of your site's header.
As you can see in the preceding screenshot, my header doesn't feature anything fancy at the moment, just the name (Daily Cooking) and the tagline (Exploring cooking every day of the week). But with just a little effort this can be changed in no time. Most themes will allow you to select any image to be placed inside the header. Twenty Thirteen has some specific requirements for this image, which you can see in the preceding screenshot. The suggested size is 1600 pixels wide by 230 pixels high, but you don't have to worry all...