Found a mobile app for fizz in the app store but it is asking for access number and password? Where can I find those details.
The only Fizz apps are to access the home wifi network and for those who use IP Relay services. You can add a shortcut on your phone to access your Fizz account.
More info on Fizz apps can be found here - https://fizz.ca/en/faq/what-are-fizz-apps
You downloaded the IP Relay services which needs the credentials
The Fizz IP Relay app is part of a whole series of measures put in place to help people with disabilities, in this case more particularly those with hearing and/or speech disorders.
If you are in the needs of this app, here the info how to obtain them.