What exactly do you want to do with the smaller pieces? Do you want to export them into smaller audio files? Generally, you can split up a longer audio object (e.g. an imported song) into smaller objects by positioning the play cursor and using the "T" key on the keyboard. If you want to create smaller audio files from a long one, you could also just do it by enclosing the part between start and end marker and using the range export option in the export function. Then move on to the next piece and repeat.
I hope this helps. Ask again if you need more detailed instructions, but make sure to describe exactly what you're trying to accomplish.