You are free to edit the site without creating an account, but if you're interested in doing more than just a few random edits, getting an account can be very useful. It's a [[Special:Userlogin|painless process]], it allows other editors on the site to get to know you better (for example, seeing where your interests lie), and gives you access to additional features.
http: //en.wikipedia.org/wiki/Wikipedia: Why_create_an_account? Why create an account?] on wikipedia for more about account creation.
==How to Contribute==