If you're logged in
Click on the Settings icon at the bottom of the left-hand navigation menu
Click on the Login link
Complete the fields Current password, New password, Confirm password
Click on the Change my password link to save your changes
If you're not logged in
From the login page :
Click on I forgot my password
Fill in your email and validate
You should receive an email to create a new password
Click Create a new password in the email
Choose your new password