To create or reset your password, login to your account at xapo.com, click on the circular avatar in the upper right hand corner, then click on "Security Settings". In your security settings, under "Password" click "Set Password" to create a password. If you've already created a password, click "Reset Password" if you forgot your password. This will start the process to reset your password - you will receive the email to reset your password 24 hours later and will receive a couple of alert emails in between for security purposes.
You can cancel the request anytime from the alert emails. If you remember your old password, you can click "Change Password" and change your password without the need to wait for the reset link.