Greetings Admiral, do you mean you still use the launcher version? Please make sure to check your email that you specified on purchase, there should be a mail from Xsolla with the Steam key. Make sure to check spam/junk folders as well.
If you can't find your Steam key there, please send me a mail on ink@navalaction.com from the email address that was used to purchase the game.
Here is guide on how to install and use Steam