Manga is generally published in a much different format than American comics. Manga is usually much smaller and collected in small volumes. They appear like small books, closer in appearance to the Archie Digests. In Japan, Manga is first published in Manga magazines that collect different stories. If certain ones get really popular, then the stories are collected and published in a new volume. Many times, the Manga has a large amount of work already published, as in the case of the popular Naruto, which has just begun to make a splash here in America.
The image below shows how you should read Manga. Follow the numbers for the panels and the text boxes to get the flow of reading Manga. At first it can be confusing, but don't worry, it will come easier over time and practice.