Need to know how to substitute shortening...

Shortening vs Butter
I found this on the food network: Substitution: Substitution: BUTTER  1 cup (2 sticks; 16 Tbsp) = 1 cup margarine OR 7/8 cup vegetable oil, lard or vegetable shortening OR 4/5 cup strained bacon fat OR 3/4 cup strained chicken fat

From Land O'Lakes: Shortening:
1 cup butter or margarine can be substituted for 1 cup shortening. When using shortening in place of butter or margarine, 1 tablespoon milk or water for each 1/2 cup shortening used may need to be added. DO NOT substitute vegetable oil for shortening when recipe calls for melting the shortening.