How old is your tank and how big is it? I have a 300 gallon display with a nice refugium (chaeto, caulerpa, etc) and a ton of pods and I haven't been luck with either of my Mandarins. I introduced one at six months of tank maturity an another at 8 months and neither one did too well. There were plenty of pods (flashlight check at night is a good indicator) as well and I don't have any aggressive fish.
So, depending on your tank size and maturity a mandarin is a risky pursuit. I'm not saying don't go for it, but buying a few hundred or even thousand pods is no replacement for a well established population and large water volume.
If you still want to go for it, find a volume dealer that has thousands of more than one type of copepod for sale (free swimming etc) and introduce them into both your refugium and display at night (when all of your fish are sleeping or they'll go to town). Monitor the growth of the population with flashlight checks and only after a couple months would I try. Also, I think they make a copepod hut (basically a breeder) that you put in the tank and your mandarin can wait out side of for a snack.
Bottom line, mandarins are a very beautiful fish, but much like the moorish idol, they are extremely difficult to care for and IMHO better left in the ocean and out of the hobby as the failure rate in captivity is just too high
Good luck!