To retrieve a temporary password if you've forgotten yours, at the login pop up, click on the link
I forgot my password!.

This will take you to a page where you will need to input either your username OR your email address, then click the Proceed button. A temporary password will be sent to your 'real email' address.

After you've logged in using the temporary password, you can reset your password in your Control Panel. Instructions on how to do this is located at the top of each page, in the Help tab's FAQs information.