You can change your password through the web portal or the app.
Web Portal:
Click HERE to log in.
When you have logged in you select "My Profile".
From there, at the bottom of the page, you will see a link to "Reset Password".
Click the link and you will be prompted to enter a new password and also confirm it
Click "Reset Password" and it will return you to the "My Overview" page.
Through the App:
Select the three dots named "More" and "Change Password"
Enter the current password followed by your new password
Click on "Done" and you will go back to the original page.