Have you ever replaced a threaded sprocket? If so, you're familiar with most of it, the tough bit is removing the existing sprocket, then the carrier fits in it's place, in the same way (tighten it once the sprocket is on with a chainwhip, though the first couple of pedal rotations will do it anyway). If you've never removed a sprocket, there's plenty of advice for that which a search should lead you too. Once the carrier is on, the sprocket slides on and there's just the snap ring. There's a bit of a technique, I'm not the most skilled at that, sometimes it pops straight on, other times it takes a few goes.
Tips - Put something on the carrier threads to ease removal if you ever need to, threadlock, copperslip, grease, whatever you have just don't put it on dry. Have a sacrificial screwdrivers to lever the snap ring on, but don't wreck a decent one. It doesn't need much force to get it on, don't overdo it, if it doesn't pop straight on, leave it 5 min and try again (That works for me, anyway!)
