For sloe gin, pour boiling water over them and leave overnight, then rinse them well. Throw the water away! Each sloe should be pierced with a cocktail stick or small sharp point like a fork!
For wine --Rinse them well before you use them and then we usually pour boiling water over them and leave them to soak for a few minutes before use. Just cover them with water and you can use the water in the wine
There's a recipe for Sloe Wine Here
Recipe for Sloe Gin Here