So i just decided to start speedrunning and i found a game but there arent any speedruns of it and i dont know how to do it

What do you meant by "arent any speedruns of it"? are you talking about a game that doesn't have any speedrun page of it?

If that's what you're talking about, then you can request the game that you want to speedrun of, via this link: https://www.speedrun.com/requestgame

Keep in mind that your account needs to be 7 days old (or above), and having at least 2 social media added to your account. Also, you need to specify the game and the speedrun aspect of the game via description and the video that you'll be submitting. Not only that, your submitted game needs to follow respective submission rules that follows ( you can find it here: https://www.speedrun.com/gamerequestrules )