How to write SQL query in to Propel Query?

Question

I have following query in SQL.

SELECT * FROM sf_product LEFT JOIN sf_product_m ON  sf_product_m.ref_m_id = sf_product.id LEFT JOIN ref_m  ON ref_m.id = sf_product_m.ref_m_id;

I'm new to propel and I have no idea how to do this in propel.