How do leaderboards work?

How do leaderboards work? I was looking at but I still don't get how to make all the functions show up. Help please.

Here is a file with all the basic funtions


It basicaly shows how to make a leaderboard


NOTE: this one doesnt have the If player equal not too player then remove from board, because its best to start simple


Heres how do understand:
Step 1:
U must set up the leaderboard to add alll the players and what ever else on....and u gota show it off course

Step 2:
Once its up and running u must make an update trigger this one runs off kills you get for killing enemy heroes.

Step 3:
Add additional functions like teams and player colours etc (optional)