Ok, Translocator usage 101:
The Translocator is one of your weapons. You can go into your configuration area and specify a key for it, so you don't have to cycle through them all to find it. I suggest mapping one key to call up Translocator directly, and one key for Select Best Weapon to get you back to a weapon as soon as you get where you're going.
You fire the Translocator and it shoots off a harmless little thingie. When you alt-fire, you appear where the thingie is, unless there physically isn't room for you where it ended up. If you fire and don't like where it went, click the fire button again and it vanishes, then you can fire again.
The translocator is vulnerable to attack. If you fire it, and then it takes damage, don't try to relocate or you die. I was playing on muttley's server and these translocators would keep mysteriously falling into the rocket-launcher pool, so I'd shoot 'em with a rocket. A little bit later the owner (Engineer, to be specific) would try to relocate and ended up dying.
If you translocate into the spot where someone's standing, they die. For bots crouching and firing at you with a slow-firing weapon like the Lightning Gun or Minigun, this is the fastest way to deal with them, and saves you ammo too. Humans are harder because they won't hold still, darn it!