You can change your PIN/Password on the security tab under your user profile. To access your user profile, click on your name at the very top of the screen.
This will redirect you to your user profile. Once there, click on the security tab on the user profile dashboard. The security tab is the second tab on your user profile dashboard.
Once there, click on the edit button at the top right corner of the screen. This will take you to a page where you can edit your PIN/Password.
After making all the necessary edits to your PIN/Password, click on the save icon at the top right corner of the screen to save your edits. Once done, you should be able to log in using your new password or check in using your new PIN.