You're taught from the ground up, no previous experience required or necessary. If you're in Phase 1, concentrate on that, if you haven't joined yet, don't try to run before you can walk, you have to get through Phase 1 first so just practise your ironing and keeping fit.
Theres very little you can prepare for in WE Phase two, its still Faraday course which means multiple choice question and answer computer based teaching. You cant find the material outside of Collingwood which the majority of it is based on.
There is a Mathematics module during the WE course which is 5 days if I remember rightly, even that wasn't very difficult and you do enough basic maths in that module to prepare you for the passing exam for it.
Only thing I can think of is to brush up on Ohms law, maybe look into working out calculating power triangles and power factors for circuits as well as voltages, DC and AC related things.
If you have not yet joined, you might want to learn/practice soldering and multi-meter use on electrical circuits - CAREFULLY......if you are not used to it. Electricity is perfectly safe until you forget that it can kill you.
Otherwise, as said above, learn the resistor colour code, series and parallel circuits and try VIR triangles and stuff.
Also find out what a WNBS is, as you will use that A LOT!!!