Assuming you are using VSDL and replacing both the openreach modem and the homehub please follow below steps to setup internet.

Password: <blank or anything>
VLAN: 101
VPI: 1
VCI: 32

Connected via the ADSL / VDSL port on the router, (grey socket?), direct to the openreach master socket using the RJ11 to RJ11 cable supplied with the Zyxel router.