There are two ways to do this:
1. If you are not logged in, you can use the "Reset password" function on the login page:
2. If you are already logged in, you can click on your name in the upper right corner and then on "Profile". This will take you to your personal profile. On the left side you will find the "Security" section.
There you can change your password by clicking on the pencil at the end of the line. Enter your new password twice followed by your current password.