An episodic series may not have an overarching story, but each 'episode' should still have a 'story' in some way, or some sense of direction; it should head towards some conclusion, even if it's the punchline of a joke. I don't think I've ever seen an interesting work that's completely directionless.
So then, you can condense each 'episode', which you do the same way as condensing any other story (identify the 'plot' of the episode and make sure every scene progresses it or contributes necessary information to understand it, preferably both). I suggest doing this anyway, because a tight/condensed story is not only less work for you but also more engaging for the reader because there are no boring/unnecessary bits.
If after this you still feel like your overall series is too long, you'll just have to throw away some episodes wholesale. If your series is completely episodic, it shouldn't matter too much which episodes you throw out since it won't interfere with continuity.