For both Android and Apple iOS you can download the "Rocket Chat" app in their associated App Store.
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When 
When downloaded, installed and started on your device, select "connect to server"
Workspace URL: chat.cept.org
User credentials:
Email or username
Password
You will find the chat username and password on your CEPT user profile page, near the bottom:
https://www.cept.org/ecc/start-page/profile/
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It is possible to change the password directly on the Chat system by either using "Forgot password" on the login form, or in the profile settings on the chat system.
Please note - by changing the password directly in the chat system, this will invalidate the password shown at the profile settings on the CEPT portal.