Hi Karl. You're right, it's not straightforwards - there's a list of effects here (
http://www.tascamforums.com/threads/dp24-32-fx-definitive-summary-of-effects.4162/), and it's quite a mixture. There is only one obvious effect called Reverb, but that's a Send effect so you can't record it at the same time as recording the vocal; the only effects you can record 'live' are Insert effects (although see Update at end of post).
You can still use the Send reverb as a comfort effect for the vocalist(s) during recording, but this won't be recorded.
There are 2 other possibilities via the Insert(Guitar) effects - the Delay effect or the Amp reverb, so if these are good enough for you then you can record these live.
The only other way is to use Bounce to 'mix' the pre-recorded vocal track(s) to another free track with reverb added via Send-1. This is obviously an off-line process, but it does give you the chance to redo the reverb if it doesn't sound right. You could commit the reverb balance at bounce time by recording both the dry and wet signals, or you could just record the wet reverb effect and leave the balance till later.
Update: Have just tried connecting the monitor output to a spare input and managed to record a Send reverb effect live. A stereo output would also work. You have to be very careful you don't get feedback (I accept no responsibility for blown speakers/eardrums!), but it is a crude way round the problem.