Hi, MM (Modular Modules) allows you to write new module just by defining database models. So you should create new module "faqs" and model "faq_question" and "faq_category". Model "faq_question" has properties "question", "answer" and related property "faq_category". Model "faq_category" has property "title". More info about MM http://dev.ikfsystems.sk/ikfa/user_guide/general/mm.html
This app is standalone admin interface web app, which work with your existing mysql database, so there is no need for integration with any existing apps. Mysql is only one junction point between admin interface and your app, but DB models/tables have to compatible naming conventions.
You can write frontend on this app also, I provide basic structure and pages module has frontend controller, you can reuse DB models etc, but it is just draft. I focus on admin part because frontend I use only on small simple (presentation) sites.