Overview
This article explains how to enable a Teams user for call recording as a Smarsh Call Recording & Analytics (CallCabinet) Agent.
Prerequisites
You will need to have already configured the CallCabinet Azure Bot and CallCabinet Teams Compliance Recording Policy using the Installer Script in this article:
How To Setup CallCabinet for Teams Customers with Installer
Enabling Teams Users with CallCabinet/Smarsh Recording
Once your Administrator has completed setup of CallCabinet in your O365/Teams tenant, they will then need to determine who is to be enabled for CallCabinet/Smarsh Call Recording by following these steps:
Navigate to your Entra ID Admin Center: (https://entra.microsoft.com)
Under “Entra ID” on the left, click on “Groups:
3. Select “All Groups”, then search for the name you gave the CallCabinet Security Group during the Installer process (This will be “CallCabinetRecordingGroup” if you did not change the default name the Installer gives you).
4. Once you have the CallCabinet Security Group open, under Manage click on “Members”, then click “+Add Members” and add the users with Teams phone numbers that you wish to be enabled for recording. Make sure to Save/Confirm once you have added all the users you wish to add. 
5. Refresh to make sure that the users have been added, then have the users make or receive at least one Teams phone call to ensure their calls are recording, then check your CallCabinet portal to not only ensure the user has pushed over as an Agent/Extension combo, but also that their calls now show up under the “Call Listing” Tab:
Smarsh/CallCabinet also has a video walkthrough on setting this up (replace “Azure Active Directory” with Entra ID Admin Center”):
How to setup users in your Azure portal