Sure, no problem.
If you take your disc (any disc) and pop it in, then select an episode (I've picked Amazon Women in the Mood), then you go to the language menu:
Then click on the "Audio Commentary" option and that should toggle it to on:
It can be quite frustrating, as sometimes it won't register it's been turned on. If you're watching them on a computer through PowerDVD you can also change the audio track by playing an episode, right-clicking on the screen and selecting Audio->English 2.
I hope this helps.