Find a layout on your helmet so that everything fits and the lights are aimed correctly. I needed to jack up the front light so it would go ahead of the bike properly. If you test this aim standing at home, keep in mind that your head will likely be bent down more on your bike if your handle bars are fairly low.
Resist the temptation to modify your helmet itself to fit the lights as it will weaken the structure. If you use glue other than mounting tape, make sure it is compatible with the helmet material.