When you open the app downloaded on your device, you are prompted "No connections found, please add a connection."

Tap Add Connection and configure the connection settings accordingly.

After saving and returning to the Connections form, you are prompted to sign in using your D365 credentials. You must have a work user configured for this to authenticate.

After confirming your credentials, confirm the environment you are connecting to.

If the authentication passes your credentials, you are returned to the home screen.