So I downloaded Livesplit from the official website, how do I configure it? I'm new to speedrunning btw.

you can download the split configure for your game in this website resource, just search the game that you wanted so you don't have to set your own split, but if you can't find the game just use the timer in livesplit, i'm new here too and already submitted speedrun

https://livesplit.org/introduction/