First, go to your phone store and search for "8x8 Work". The app has following branding:
Sign into phone app using SSO. As long as you know your Microsoft password and have Authenticator app, you should be good. If not, please contact helpdesk@meridian.org.
Once access is complete, see videos below for quick tutorial.
For additional information see 8x8 Work for Mobile Quick User Guide - 8x8 Work for Mobile | 8x8