Here we go. Simple rules.
Everyone gets 3 Tokens. With these three tokens you can do the following.
1. Switch an ability of any existing Pokemon.
2. Obtain a new non-legendary XY Pokemon.
3. Evolve any Pokemon to its next stage with no exp.
So you can get 3 new XY folks, or evolve one XY to its final level, or just upgrade your current team with new Abilities..or what have you
These tokens do expire, so you have until Oct 24th to use them up.
By that time, the Tower will be up and running with the prices for Pokemon.
So, start it up!