I'm planning to design a website which allows users to register and log into the system. My idea is that when the user logs into the system, he will be redirected to selfoss (a single-user RSS reader) and he can customise it based on his needs.

Although I have successfully implemented the user registration and login system, I have no idea how to implement the latter, which is to turn selfoss (single-based) into a multiple-user platform where each user can only access his own customised RSS reader when logging in. So, when the user logs into the system next time, all his previous settings for that customised RSS reader will also be reloaded.

Can I have some references and guidance on the implementation of such system? Thanks in advance!