1) Open iTunes
2) Click on TV Shows
3) Scroll down to the bottom of the middle column to where you see Free on iTunes.
4) Click on See All
Click through the pages to find the episodes. I believe there are about seven episodes (green covers). You can also find the same ones in English (purple covers). Perhaps you and your children could watch an episode in English first, then watch the Spanish version. Did I mention that they were free as in gratis?
To download iTunes, click here. You will need an iTunes account in order to download from the store. Account registration is free, but may require a valid credit card.