Hi Dany,
OpenWISP WiFi Login Pages is not a replacemente for a captive portal. OpenWISP WiFi Login Pages is a replacement for the system which is shown after the captive portal redirects the user to a specific website which asks the user to sign up, hence it's totally optional because some WiFi systems may not require sign up at all.
Whether you need users to sign up or not, if you want to show a webpage to your users when they connect to the WiFi, you'll need a captive portal software which handles the firewall rules.
For the rest, your request for help is too generic for me to help you out.
When we'll have a chance to write a full step by step tutorial we'll do it, for the moment I can only recommend to ask more detailed questions.
Best regards
Federico