Once you have enough credits in your account (click here for more information), you can download sounds by clicking on the download icon on the far right of the sound when displayed.
You can also download entire packs by clicking on the download icon displayed next to the pack's cover art at top of the page.
To download custom batches of sounds and samples, you can add those files to your Drives and download them all at once. For more information on Drives, click here.