Create and Integrate SQL database files

Greetings. I am new to Local, and I am also new to website building. I am trying to build the support page and login page. I am trying to store the username and passwords. What file type would I use? I am assuming that I would use SQL files. How would I create and integrate them into Local? I a runnning Linux Mint 19.2. I know I am asking for a lot. Any help is very much appreciated.