You can define a new password at any time without knowing your old password. However, you do need access to your email account to complete the process.
On the login screen, click on the link below the login fields:
Then enter your login email address:
Go to that email account to get a link. The message will come from email@example.com. If you do not receive an email, it might be stuck in a filter. Please check your SPAM or JUNK folder. This is also a good time to remind you to add firstname.lastname@example.org to your address book.
When you click on the link, you will be prompted to define a new password: