Larry, I poked through the settings real fast to see if i could find what you're looking for, and I don't see it. That being said, I think Awasu already checks for updates when you start it. At least it does for me. When you set up a channel you tell it how frequently you want it update. As far as i can tell, if the timer has elapsed since the last time you opened Awasu, it checks the feed.
For instance, most of my channels are set to update once ever 6 hours. A few are set for one or 2 hours if they're more regularly updated. When i launch Awasu each morning, it checks all of my channels. I don't have to manually tell it to update.
If you're channels aren't updating then it may be because you've indicated a "blackout" schedule where the program is supposed to refrain from updating. Or perhaps somehow, you've not specified an update schedule for the channel. (Though i don't expect this is the problem, since "never" isn't one of the update options).