If it's your first time speedrunning a game, what do you do with the timers for the sections?

Hmm? If you’ve set up your segments in LiveSplit or its equivalent, they’ll be blank until you do your first run. They don’t fill in until you complete a run and actually split for each segment.

first you download a timer like livesplit and if you head to the speedrun page for the game you are running chances are there will be a "resources" section and it may have the splits setup for you :)

I use a Mac computer and I can't run LiveSplit with Wine.

Look in here: https://www.speedrun.com/resources

I chose Time Split Tracker for my timer.

I would recommend Llanfair for the browser version of LibeSplit called LiveSplitOne as those are the most popular Mac timers. Idk what that program is you downloaded so I have no input on that.