If you have snails in your aquarium, they are essentially in there forever. They will be in your filtration, they will have laid eggs in your plants, so you will have new snails going forward. All you can really do is control numbers. Don't overfeed your fish to ensure there isn't an abundant food source to support excess numbers. Manually remove them as you see them, you can crush them against the glass, fashion traps with bait and remove them, you can put a lettuce leaf in, and remove it after it's attracted a number of snails. I'd personally kill them once removed. I wouldn't release them for fear that they are a non native species or that they are carrying some kind of disease or parasite that isn't naturally present.
There are fish that eat snails. Loaches for instance. Assassin snails will eat them too. But as they will already be in the workings of your system these aren't likely to completely eradicate.
There are chemical treatments that should kill them, but these treatments will kill all invertebrates, and you won't be able to get rid of the chemicals once they are in your aquarium as they will soak into filter media, driftwoodll, rock etc. So even if you don't have other inverts, you could never have them going forward either if you chemically kill them.