If you have designed, developed and launched a game and want to market it, here are some strategies:

Influencer Marketing
You can pay gaming influencers to talk about your game on their channel. This might influence the subscribers of these influencers to play your game.

PR
You can reach out to gaming websites, gaming influencers and streamers and ask them to feature your game in their content or maybe even review your game in their content.

ASO
Just like SEO for blogs and websites, ASO (App Store Optimization) helps your app become more visible and thus reach more users. You can put relevant keywords in the game description and attach high quality screenshots of your game to increase ASO and thus increase the number of downloads of your game.

SMM
Social media marketing is another great way to market your game. You can use your own social media handles to promote your game. You can also try to build a following on various social media platforms by posting content regularly so that your game reaches maximum number of people possible. Ideally, you could post content regarding tech, entrepreneurship, gaming etc since you have created a game and want players to experience it.