You can change the 'title' tag - in whatever method you used to make your podcast there will be a place where you originally entered the title and you can change it there.
You need to be careful about this. Some methods - iWeb included - make the title part of the feed URL, so if you change the title you will change the URL, and your podcast will stop working. It's sometimes possible to get round this, but it's a bit of a fiddle.
It would probably be useful if you posted your feed URL: I can advise whether changing the title is likely to be a problem and if so whether it's possible to do anything about it.