Introduced in RIFTS: England (of all things), Temporal Magic enters the game through the Temporal Raider Racial Occupation (not playable as-written) and its two playable Occupations: the Temporal Wizard and the Temporal Warrior. Alas, those looking to get their Time Lord on will be sadly disappointed.
These two Occupations are unique in that a player may opt to enter play above 1st level, but at the price of a restriction in his character's Alignment options (downward, of course) and sanity (also downward). The options are to represent the effects that the Wizard or Warrior sustains from his association with the Raider that trained him, who is a universally evil and abusive entity that cannot help but to corrode the character of his mortal associates if they stay too long. The benefit, of course, is more power and the other benefits of being higher level (which, this being a Palladium game, aren't that great). Quite frankly, it's a bad deal; don't do it.
These Occupations are supposed to be all about time travel and time manipulation, but the spells at their disposal are weaksauce; this is because, quite frankly, player access to such things cannot help but to take a campaign and turn it into a Time War due to players wanting to make the most of the time manipulation powers at their disposal as well as time travel traditionally being just a MacGuffin used to set a story in whatever genre that the writer wanted to mess with in that story. (As so well demonstrated by Doctor Who, of course.) Instead, the time powers at a player's command tend toward the tactical end of things with some provision for forward travel through time and (oddly) dimensional manipulation (i.e. appearing as a 2D image so one can go flush along a wall). This is unlikely to satisfy anyone who would be interested in either of these Occupations.
So, how to play them? You should look at the Wizard as being a technician focused on the manipulation of time in the same way that a IT specialist is a technician that focuses on some form of computer or network technology, and the Warrior as being a Magic Knight with a time theme to his wiggly-fingers stuff (and that, in turn, being more like the magical martial arts of a wuxia film or the Jedi arts of Star Wars). (The powers of the Raider are vaguely defined, as one would expect of something intended to be just a NPC, but are said to be far more powerful.) Both Occupations are not proper scientists or engineers that grok Temporal power at a core principle level; they're limited to applied comprehension, at best, and it would not be wrong to think of them as being a tool-user/maintainer caste meant to be under Raider supervision most of the time. This would account for their weaksauce abilities in comparison to expectations.
While Shifters and Stone Masters often end up as NPCs due to logistics, I expect these Occupations (and the Raider) to be primarily NPC or not appearing at all because--quite frankly--they suck. They suck enough I recommend against including them at all, and I recommend instead just rolling your own Time Lord RCC because that's what you really want anyway.