How would I got about making a signup/login? Database help!

Need help making a login/signup function, as well as a menu in general to input said information. Nothing fancy, just username and password. Would also like to add a scoreboard for the top 10 quickest time all targets are shot. How would I go about connecting a database to this? As well as adding a visible timer during the game? Firebase, MySQL, whatever is easiest with PlayCanvas. How would I also go about making a menu before the game starts? Explain like I’m 10 :).

https://playcanvas.com/project/1273597/overview/final