Jon,
Honestly, it depends on your tank and what is in your tank as to whether they will live and thrive.
If you have good water quality, lots of LR, and few predators (ie - copepod eating fish such as a mandarin), then odds are they will thrive. I have no fuge, and I have lots of copepods and amphipods, although probbaly not enough(55 gallon tank) to sustain a mandarin in then long term.
How you get them...well, odds are you already have them. They come in your LR etc, and when conditions are right (water, maturity, food source, predation etc) they will start to thrive. So basically, time and patience, and some tank planning. You may want to try sneaking a peek at your tank after the lights have been out for a while. USe a flashlight, and I am sure you will see some little things scampering around...those are probably amphipods.
UNlike G-Dude, I have never seen live copepods for sale at a LFS, although I have read about places online that you can order them from to jump start your population. However, if the conditions are not right in your tank, they will not thrive, so depending on your situation, it is probably better to wait until you population takes off on its own.
HTH
Stewart
