JOIN Multi-table

need your help on this please.

I’m trying to JOIN Purchasing.PurchaseOrderHeader table

INTO this query.

 SELECT pp.LastName, pp.FirstName, ss.SalesYTD  FROM Person.Person pp  JOIN Sales.SalesPerson ss  ON pp.BusinessEntityID=ss.BusinessEntityID; 

Trying to add EmployeeID, SUM(TotalDue) WHERE Orderdate is 2013 on the same column as SalesYTD

Here are my tables. enter image description here

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