Well, there's a couple of ways. Some companies reccomend you take off the old gauges and needles and replace them with the new gauges and put the needles back on. Those are old indiglow gauges that tends to put out heat. Plus, it's a pain to put the needles back in the correct spot. Especially the speedo needle. THe tach, temp, & fuel needles are a little easier. You can remember the correct spot for those during normal operating temperature. Other companies reccomend you just slide the gauges over the needles and on top of the stock gauges. There are a few reasons for this
1) It's much simplier
2) They don't heat up as much as the older ones
3)You don't have to remove the needles

After that, everything is pretty easy. Just connect the gauges to the supplied power supply, and connect the two wires from the power supply (pos/neg) to the proper source. When I connected mine, I simply ran the positive to a spot in the fuse box that is activated when the key is in the "ON" position. then simply ground the negative and you're done. Here's a few pics of mine