Creating a Wikipedia account has many benefits! For example, users with accounts have the ability to start new pages, edit semi-protected pages, rename pages, and upload images. Other benefits include having your own user page, a personal watchlist, the ability to implement a plethora of gadgets, and the potential to become an administrator!
To create an account, all you have to do is click on the "Sign in / create account" link, click on "Create one", enter a username, a password (twice), then click the "Create account" button. Consider attaching an email address to your account for user account password recovery, to receive system updates, or to receive email from other users. Nobody will see your email address until you choose to send them an email or reply to theirs.