I see i can download individual podcasts one by one but i can't figure out how to subscribe to an entire podcast going forward on my ipod touch.
is this possible or can you only do this from itunes on your computer??
As far as I know, you can't subscribe to them from your iTunes app on your iPod.
The easiest way I know of is to subscribe to whatever podcast you want to listen to in your preferred feed reader, and then whenever that podcast is updated you'll see it in your feed. From there you can just choose to play or download it. Hopefully this helps solve your issue.
Although it doesn't integrate with iTunes, Instacast will let you subscribe and download new episodes to podcasts.