How to write simple trigger

DECLARE @OrgID AS NVARCHAR(10)
DECLARE @OrgName AS NVARCHAR(50)
DECLARE @Sql AS NVARCHAR(MAX)

DECLARE cursor_org CURSOR
FOR
SELECT ID
 ,NAME
FROM Aareasmaster.dbo.Organization_Structure
WHERE (UseCommonSite = 1)
 AND ID = 253

OPEN cursor_org

FETCH NEXT
FROM cursor_org
INTO @OrgID
 ,@OrgName

WHILE @@fetch_status = 0
BEGIN
 SET @Sql = N'
 DELETE Aareasmaster.dbo.Organization_Users WHERE OrganizationID = ' + @OrgID + '
 INSERT INTO Aareasmaster.dbo.Organization_Users (
  Username
  ,Token
  ,OrganizationID
  ,[Timestamp]
  )
 SELECT Username
  ,NULL Token
  ,' + @OrgID + ' OrganizationID
  ,getdate() [Timestamp]
 FROM ' + @OrgName + N'.dbo.Contacts
 WHERE (Contact_Type = ''E'')'

 EXECUTE sp_executesql @Sql

 --PRINT @Sql
 FETCH NEXT
 FROM cursor_org
 INTO @OrgID
  ,@OrgName
END

CLOSE cursor_org

DEALLOCATE cursor_org