Your mic should have come with some kind of instructions for this. Was there a particular reason you bought a dual capsule microphone? There really isn't much use for the figure 8 for solo vocals. Now, for singing 'in the round' the figure 8 pattern can be quite a boon.

One thing is certain, you don't want to put sources on the 'sides' of the 8 (as viewed from above).

Which microphone is it by the way?

-Scott