What
This article explains how to enable Microsoft Teams integration with Mercury.
NOTE: The instructions in this article can only be carried out by your organisation's System Administrator.
Where
Microsoft Dynamics 365 Sales Hub > App Settings > General Settings
How
NOTE: You must be a global administrator (tenant administrator) to enable Teams chat. Ater that, system administrators can configure Teams chat accordingly.
1. In the Sales Hub app, select Change area 
in the lower-left corner, and then select App Settings.
2. Under General Settings select Chat and collaborate.
3. Turn on the Turn on Microsoft Teams chats inside Dynamics 365 toggle.
4. Save the changes.
The integration is now enabled. You can try opening an appropriate record in Mercury and verify whether you're able to access Microsoft Teams within the record, and view the chats related to that record.
Additional information
For more supporting information regarding this feature, please refer to this Microsoft article.