Note: If you've lost your password and can't access your account, there's a specific article that explains how to recover your password: Read article here
Changing your password is a good security habit. Here's how you can do it.
1 - Open your user profile by clicking on your name at the top right of the screen
2 - Click on the Password tab at the top
3 - Fill in the fields asking for your new password
4 - Don't forget to save