For Shared hosting accounts:
To change your cPanel password simply login to your GlowHost Account Manager located here. Once logged in, click 'Manage My Domains' in the navigation bar. Once that page loads, you will see your control panel information and an option to change your cPanel password.
For Reseller, Dedicated and VPS accounts:
Please refer to the official cPanel and WHM documentation.
cPanel - WHM official Documentation
Essentially, you can do this in the user's cPanel using the password change option on in WHM > Account Functions > Password Modification.