The "inputs" selection in your recording program for each track should show a choice of Left, Right and Stereo for each stereo pair. For ex., Delta 1/2 Left, Delta 1/2 Right, and Delta 1/2 Stereo. Same for the Delta 3/4.
For each stereo pair (1/2, 3/4) the odd number will be the left input and the even number is the right input.
To record four tracks at once you should select Delta 1/2 Left for Track One. Then select Delta 1/2 Right for Track Two. Same for Tracks 3 and 4, using the 3/4 left and right.
Then connect four mono sources into your Delta in inputs 1, 2, 3, and 4. If you've set it up as I described above, whatever is plugged into Input 1 should record on Track 1.
The numbers don't have to match. You can record from input 4 on Track One also. In that case the Track One input selection should be Delta 3/4 Right.
Comprende?