Changing tempo of a loop

hello guys,
i am new to this audio editing/recording. i am working on cubase 5. i need help with changing the tempo of a particular loop. for eg. i add a loop into my project by drag and drop and i find it too fast. now i intend to change the tempo of that particular beat so that i can sing on the tempo i want. i try changing the tempo by going to tempo track and reducing the tempo but there is no effect of the changes i make to the tempo of the loop i added to my project. someone please help me.