How do you connect a database to a webpage?

How do I take my code and have it send information to my database?

I've been restling with this problem for a month too long. Here's what I have:

I have a very simple bit of code for a webpage and I want to attach it to a database so I can save anything I 'post' right on the webpage. It's your standard 'save' button, except I can't link my button to my database. I'm using SQLite for the database, and a mixture of HTML5, JavaScript, and CSS for the webpage itself. In short, I'm building a webpage from scratch (running on localhost) as a personal project, and I want to be able to save it to something.

I've followed a couple of leads on CodeIgniter, SQLite.org, and digitalocean, but found nothing relating to my specific problem. I have created several databases through terminal, and saved them to disk space rather than RAM so I could close terminal without losing my progress. I have also been able to add information to the database in terminal, so I think I have a half-decent grasp on database management.

If anyone has suggestions, I would love to hear them.

Thanks a million.