Assign Capacity to Workspace

I wanted to assign a PowerBI embedded capacity to an existing Workspace using the API. 

1. Created a PowerBI embedded capacity in Azure and added the service principal as Capacity Administrator
2. The Groups AssignToCapacity API requires to pass the CapacityId. I have no clue on where to get the CapacityId from.
3. Checked Azure portal on the created PowerBI embedded capacity and that doesn't have any Id (or atleast not shown in its properties)

Can you please guide me on where to get the CapacityId from that can be passes to the AssignToCapacity API?

Thanks!