Whenever I first visit a wiki-powered website, I am often faced with this same confusion. When Tim Burners-Lee originally conceptualized the idea of hyperlinks, his belief was that it would lead to a new way of reading, where the goal-oriented linear method would succumb to more of a random walk. I never did like the straight and narrow, so don't be a afraid to leave the beaten path.
For those of you who do need a beginning to an end, you can check out the starting points listed on the start page. Otherwise, try making use of the search or any hyperlinked words you see. You might be suprised where it takes you. At any point, if you want to go back to one of previous pages in your walk, simply use the cookie crumb navigation at the top of the page. Another way to "get back" is to click on the wiki page name, which appears as a link in the upper left corner of the page. This link will show you a list of backlinks, or pages that link to the page you are on.
If you would like to contribute, please read the syntax page for more information about how to add content to this type of website. Before creating a page, head over to the playground to try things out.