This is going to be generic to getting in and out of a recording setup-
You're going to need to look at your software output options- to let your pre recorded mono vocal track either be assigned directly to one of the two Alesis 1/4" outs (likely one that is normally connected to your main playback amp or speakers) and reconnect it to the line in on the effects.
If you can't assign the track directly out you may just play only that track (solo it, mute, turn down the others, whatever) so only it feeds through the normal master out- to the effect.
Get that worked out, the levels in the software must not exceed 'zero/full output'- no clipping allowed, then set for normal level at the effect's input, and the effect's wet/dry output mix to 100% effected.
Connect the two outs on the effect (..or one if that's all you need) to your two Alesis inputs, make a new pair of tracks (or a stereo track if you like) to record the effect.
Do some tests runs, set for normal record level.. and nail it.
There is a potential for a feed back loop here so the new 'effects record' tracks must not play into the master if that's the route you take, during the recording -turn their faders down/off..
The blend of your new effects tracks are your effects balance control.
If you have only two outs- the 'master outs, it's going to be harder to dial the effects in in real time prior to recording them. You could test sing into the Helicon to set it up, either mic-in, or perhaps use the insert?, then record it?
You may be able to go digital SPDIF out and/or back in instead of taking up the analog master outs, I don't know, but it might be a good option (cleaner, less hassle using up your monitor path etc!
I think that covers it. Probably not..

Go for it.
.. it gets easier as you go.