Hi this issue has since been resolved.
When the organisation has opted in, this feature should be available for all users in the tenant.
Please don't hesitate to get in touch should you have any further queries.
Thanks for the inquiry and the image.
An administrator can opt-in on behalf of all users in your organization.
To do so, please ask your admin to select an email to be saved, select OnePlaceMail and select the three bars on the top right hand side.
Select "Settings" Under Optional features, here a link will appear to allow your admin to opt in and select "Accept".
Users will then be able to save emails to a Microsoft Teams channel.
Please let me know how you go.