I've put together a quick 1 minute video to cover how to install the in-game timer (IGT) used for the leaderboard.

You can see it here on Twitch:

Or here on YouTube: )

I've also added a blurb on this in the Beginner's Speedrun text guide: https://docs.google.com/document/d/17ZcCIXDQ4MBJxH7VnVxHn7F_a5Co0jMKiqNGH9olWBQ/edit?usp=sharing