Chargers are moved after compulsory movement and before you move the rest of your army. Make sure you complete all charges before moving other troops. Chargers move at double their normal movement rate, but must make the usual deductions for crossing terrain and obstacles. For example, mounted knights have a normal move of 6" and so can charge up to 12". If they are moving over difficult terrain such as a muddy field they move at half speed, reducing their charge distance to 6".
Before you move a charging unit check that the enemy has declared his response and that troops electing to flee have been moved and troops electing to stand and shoot have done so. Measure the distance between the chargers and their target.