1. Open EDMX in to Design Mode
2. Click Model Browser then type the Store procedure name on search and press Enter.
It will highlight the store procedure.
3. If you already try to add this store procedure, then in some case it create Function when you have a return value on your SP. other wise it will not create the function. remove all from function.
3. If your SP has no return type then you may can use a simple return type value like :
SELECT 1 as DefaultValue if you already have return type then you don't need that.
4. Select the Store procedure from model browser-> right click -> Add function Import.
5. Check Complex and Click Get column Information
6. Click on Create New Complex type.
7. It will create Function and complex type for that Store Procedure.
Click OK and Build your application.