Currently password reset is only available through the web. It will be added to the Hylo app in one of the next updates.
Go to https://www.hylo.com/
Click "Forgot Password" on the sign in page.
Enter your email address and click "Reset"
Log into your email and find the password reset code.
Enter the code into Hylo.
Create a new password.
If you signed up with a Google or Facebook account you must use their password resetting options.