No, you don’t. In fact, you can use scores.fiba3x3.com game directory just to enter the scores.
You can also use only some of the functions – for example, just team points and fouls - of the scoreboard. Of course, whatever you decide to do, you should consistently throughout your event.
Note that the individual points scored by individual players are taken into account in awarding the FIBA 3x3 Individual World Ranking points only if such data is collected completely from all the games of the events.