I am not exactly speaking for experience, but as the person above said you probably should have been promoting your game prior to release. But, a good place to start would be to make a trailer of your game. Watch Game Maker's toolkit's video on how to make one that's effective.
Make a YouTube channel, a Reddit account and various other social media accounts. Put the trailer on YT put the link to your trailer in any Subreddit where it would make sense and would be allowed (like the Godot subreddit). Join Discords and spread the word, post on Instagram or twitter hashtags, do everything you can online. You could, if your game is monetised, pay for advertising, but this is very expensive.
If you have access to tools to make T-shirts for your game and sell them or even just give them away I'd do that too. If people wear them, that's free advertising!