You can't add them to the "soundpool" per se. You'd have to put them in a folder (or folders by type) and use the File Manager. Using the File Manager, find the folder of your files, then you can preview them and add them to the arranger just like as if it were a soundpool.
Note: If you have the Program Settings set to "automatically adjust samples to BPM", then you will need to use the BPM Wizard in the Remix Agent to find and assign a tempo (BPM) to each of your samples. It's a very good idea no matter if you're using it or not.