Depending on Call Experience settings you may need to download the mobile app. If you need to download the mobile app, ShowMe by Blitzz, this is the icon to look for in the Apple Appstore or Google play store:
After downloading, installing, and opening the mobile app you will see the screen below and wonder where is my code?
At this point return to the Invite link that was sent to you via SMS, Email or WhatsApp and click the URL. This will fill in the code and you can now start your session: