Go to the Lower City in Act 3
Find the Devil’s Fee shop in the Lower City
Speak to Helsik, the shopkeeper
Pay her or convince her to help you open a portal to the House of Hope
Collect the required ritual items if she asks for them
Perform the ritual at the Devil’s Fee to open the portal
Enter the portal to reach the House of Hope
Alternatively, use the portal after dealing with Raphael’s questline in the Lower City if you already have access to the ritual setup