If you go to System Updates on your TouchPad you should see webOS 3.0.5 86 listed. You can either wait for it to auto-download when the device is idle, or you can click the Download Now button. (Like anyone's NOT going to click download now!)
As outlined in a previous post the 3.0.4 update never did show up for me so if you're having issues you can use webOS Doctor and update that way.
If you're interested in following all the work that's being done on webOS as they make the transition to open source be sure and follow @webosinternals on Twitter.