It is best to choose a WikiName (like FirstnameLastname) as username to get your changes and signatures link back to your WikiHomepage. Your email is needed for you to be able to get notifications on page changes and to recover lost login data.
If you click on GetText(Create Profile), a user profile will be created for you and you will be logged in immediately.
If you forgot your password, provide your email address and click on GetText(Mail me my account data).
The email you get contains the encrypted password (so even if someone intercepts the mail, he won't know your REAL password). Just copy and paste it into the login mask into the password field and log in.
Then change your password to a known value and save your settings.
GetText(Save) updates your profile (stored on the wiki server).
GetText(Logout) clears the cookie created at login.
The cookie will expire next midnight - except if you choose GetText(Remember login information) (after being logged in), then the cookie will not expire. After the cookie has expired, you have to login again.