If a member has forgotten their username or password, they can click the Forgot your username or password? link.
This will allow them to enter their username or email address into a form, which will automatically send their login details to the email address for their account.
Hint: You can edit the email which is sent to them in the Email Templates page under the Settings tab.
I'm "not authorised to view the Player Emails page" for some reason so can't see what that's about!