Creating a Stored Procedure in a Datamart?

Is this possible?  I created a datamart, and connect to it via the SQL endpoint in SSMS.  

Then in SSMS i tried to create a generic procedure with this code:

USE [db_name];  
GO  
CREATE PROCEDURE model.uspGetEmployeesTest2   
    @LastName nvarchar(50),   
    @FirstName nvarchar(50)   
AS   

    SET NOCOUNT ON;  
    SELECT *  
    FROM model.tablename
    WHERE attribute = @FirstName AND attribute2 = @LastName  
    ;  
GO  

But i just get a permission denied error.   Is there any way to grant myself permission to create this in the datamart?