Just wire it up the pot so it connects the right lug to ground (same as the volume - as viewed from under the pickguard with the lugs towards you) and the wiper to the joined black and white. Full up is humbucking and as you back off, one coil will gradually be earthed.
Also try it with the right lug connected to the hot instead of the ground (which will give you the other coil in single-coil mode). See which coil you prefer. If you are feeling
really adventurous, you can experiment with putting a cap between the right lug and ground (which lets you get some single-coil high end while keeping the lows intact for hum cancelling) - Experiment with cap values between, .01 uF and .047 uF.
Here is a Seymour Duncan diagram of the same but
NB - the wiring colour code is different - where you see the red +white, DiMarzio uses black +white:
http://www.seymourduncan.com/support/wiring-diagrams/schematics.php?schematic=1h_1v_1sas