Hello fellow programmers, I recently have made little quiz using html, css, and JS but I want to add more features like adding a username and password if the user decides to create an account. What are my next steps? Thanks.
Firstly, welcome to the forums.
While we are primarily here to help people with their Free Code Camp progress, we are open to people on other paths, too. Some of what you are asking is pretty trivial in the Free Code Camp context, so you might find that if you’re not getting the instruction and material you need in your current studies, the FCC curriculum will really help you get started. At a modest guess I’d say investing a 4-5 hours working through the curriculum here will really pay off. You can find the curriculum at https://www.freecodecamp.org/learn.
With your current questions, we don’t have enough context to know what you already know or don’t know, so it is impossible to guide you without just telling you the answer (which we won’t do).
It is pretty typical on here for people to share a codepen / repl.it / jsfiddle example of what they have tried so that anyone helping has more of an idea of what help is actually helpful.
Please provide some example of what you’ve tried and I’m sure you’ll get more help.
Happy coding 
At this moment am at the functional programming section. I know Python and C++ but at a college level if that makes sense(am still in university). So far I understand almost everything, except for the algorithm and functional sections, in those section am a little confuse. That’s why I want to work on my project so I can retain these new information better. Also I can do the tutorial for about an hour and half, after that I tend to get distracted and not concentrate properly, which is why I immediately start working on my project after it because I actually like googling or stack overflow it most of my answers. I hope this can give you a better idea
This really depends on what you are planning to do with these users. If you are going for something like register - choose username/password - save settings for next login etc. I would say you are looking at a full fledged content management system because this need a database. Very few people make these on their own these days, there are many to choose from. First you have to look at favorite programming language and something that can be hosted for a reasonable price. Then it is just googleing to make a pick.
But if you have then time there will be some fun in database design. I recommend http://dia-installer.de/ for designing databases from scratch
/Jakob