About one in fifteen people is born with the ability to use his or her anie almost the way that every able-bodied person can use his or her body. These people are called semte (plural semti), 'gifted'. It's a natural thing, much like musical talent. You can have the ability without knowing it, or know it and make no use of it because it's outside your field of interest, or use it for your own and others' benefit or enjoyment, or make a living by it.
Most people who are gifted discover it at the time that Timoine leaves them, around the onset of puberty. The usual age to start learning semsin is between eleven and fourteen. In some children, especially when the gift is very strong, it shows earlier and should be trained as soon as possible to prevent mental instability. Often, the gift is first recognised by another semte: a parent, a teacher, a passing runner on the lookout for new talent.
As soon as you know that you're gifted you will be encouraged to learn to use your gifts. You find a teacher, usually a master but sometimes a proficient journeyman, and discover what gifts you have and how to use them. How long such an apprenticeship takes varies with your ability, perseverance, and other circumstances, but usually it will be three to five years.
During this apprenticeship you learn to manage your anie the way you manage your body, and to distinguish between perceptions with the senses of your body and those of your anie. This can be very difficult for beginners; especially children who develop their gifts early tend to 'see things' and be frightened, because they can't tell that it's their mind's eye, not their physical eyes, that they see them with.
An apprentice who is ready faces his or her journeyman's trial, usually a sudden and unexpected event that can take different forms depending on the psychological makeup of the apprentice. It's always difficult but never impossible, and it can be dangerous; it's even possible to become a journeyman in a psychic fight with the enemy (they are less scrupulous than our side, and send their candidates to duel with ours).
Once you're a journeyman you have to either declare your allegiance (and become a member of the Guild of Anshen, or of the Guild of the Nameless One) or drop out altogether and receive no further instruction. Both Guilds find it far too dangerous to have unaligned highly trained semti around.