I bought the game a couple of years ago, and I have came back to it after a long time. Since then, I can't download the game again through the website, where I purchased it from. How do I get the game again?
If you bought it quite some time ago, you probably got it from itch.io. If you create an account there with your email address, it should show up in your purchases.
If that doesn't help, drop me an email at firstname.lastname@example.org with whatever info you still have about your purchase, and I'll figure things out. :)