The first thing to do is get the hardware part wired up.
I will assume you have your monitors wired from the master outs on the front end of the VS2400. Right next to the master outs are the Aux A out. Two outputs L and R, unless you plan on going in and out and back in and out in stereo, it doesn't matter which out you come from. Go from a output to the input of you TC unit. Then from the TC unit out back to an input channel on the top of the VS2400. That should take care of the hard wiring.
Now on your VS2400 screen menu go to the tab on top EZ ROUTING, then click on routing view. This will bring up the part of the internal routing to be able to get your vocal track from your VS2400 thru your TC and recorded to another track.
On the far upper right of the routing view screen, there is a button that sez DIRECT TRACK OUT, push that, it will lite up yellow. You will see all the tracks (1-24) listed in pairs along the right side, These reference your recorded tracks.At the top where it sez ANALOG MULTI OUTPUT, picture this as a representation of the back of the VS2400(because that is what it is) the outputs 1-2 are your main outs, 3-4 are you aux outs. If you are coming out of 3, then you can come out of any of the odd # channels, and 4 would be even channels. In other words, If your vocal track is recorded on track 10, you need to have it hard wired from the VS aux outs from 4 (the right) 3 - 4 are labeled left and right on the top of the VS.
Just as an example I will say the vocal track is on 10. You would want to move the virtual cables on the screen from the default position of channels 5-6 (on the right) down to the 9-10 position. This is when how you have the output hard wired matters. ALL of this is just ins and outs. That is the most logical way to think of it. So now you have it set up for your vocal track to go out of the VS in to your TC back out to a input channel. For example, you plug it in channel 5, You now have to arm that channel to record, turn the input level up(just think of it as recording another instrument) On the Routing screen you have to change the virtual cables to monitor the track you are recording to. For my example, drag down the pair from the default position from track 1-2 to 5-6. You do this to monitor what you are recording . If you had this senerio set up, when you went to record, you would hear tracks 5 and 6. 6 may be someting else, but 5 would be what you where recording to. It always comes across in pairs odd is left and even is right, when you are recording like this (unless stereo) you will only hear the one side (L or R)
Very important, turn the amp down on your monitors (or if active monitors, turn there volume down)when you are recording like this, the master volume does not work, the incoming level is based on the out going level of the original track. If the signal path is set up correctly, you should be able to hit record and hear just the vocal track in one channel and adjust the TC unit and hear the changes. After you record the effected track, to hear everything again, you have to go back to the routing view and and hit the yellow track direct out button to off. Well, I read this and I'm confused, I do this all the time and it's not that complicated, but it's strange explaining it. If you have any more questions, just ask, I will try to clearify myself. If you really look at that routing screen and picture it as ins and outs, it starts to make more sense. Good Luck!
Doug