Edit third party script and ad extra functions (small project)

We have a website which allows us to upload online content through a system created on PHP and SQL. This system is connected to a database of a Paid Forum (Invision Power Board), which works with exclusive tables. We want to change the connection that the system has to the Invision Power Board Forum to the PHPBB Forum, then we want to add a function that will allow subscriptions and login of the users to the system by using the tables on the PHPBB Forum, and also one more function that will allow to add text content mainly (summaries). The attachment document has all detailed information about the project. The website is in Spanish, but it is not required to know or speak Spanish to do the project. There is no need to transfer existent users from the Forum that will be abandoned to the new that will be created, all registrations will start from zero.