When using an aerial with a dual feed converter to receive two satellites the parabola has to be aligned by adding a DiSEqC switch, but only after having completed the pointing.
For aerials pointed for instance on HotBird 13° east and Astra 19° east, remember that, when facing the parabola, the right-hand converter must be aligned with the HotBird satellite and connected to input 1 or A of the switch, while the left-hand with Astra and connected to input 2 or B of the switch.
If you have difficulty it would be best to contact an installer.