You don't need to tame it for it to produce Achatina paste. It will produce it in the wild on its own, so putting it in a pen close to water (wild Achatina needs to be close to water or it will die, as per the Ark wiki) will allow you to take advantage of this. Seeing as the paste is tough to see due to its size, it's recommended to build your pen on sand, or on any other terrain free from clutter.
Note that this has been only tested out on single player.
Easy way to keep them in place, just fill their inventory with stone. Encumbered, they will not move, even on wander. Then for feeding, put cake in a tough. They will stay in place and alive! Making you resources the whole time... Up to the top for knowledge!
TIPP: Achatinas can produce organic Polymer. You can just craft a fridge with the organic Polymer and destroy it. Every time you destroy a fridge you get normal Polymer back. That means you can transform organic Polymer to normal Polymer. I found it out yesterday by myself.
The achatina is a small snail, carryable by hand, that can be useful if you are missing a small amount of cementing paste, and can’t be bothered to go and get the supplies to craft more. It poops and passively generates achatina paste, which is identical functionally and visually to cementing paste. It can hold up to 100 at a time.
When tamed, the Achatina can produce Achatina paste, an alternative to cementing paste, passively when on wandering. You could also collect it when they are moving, their paste/slime will be on the ground shaped in a similar feces ball.
Will only eat Sweet Veggie Cakes even after being tamed! Each cake fills the food by about 200. Poops paste as well as prudces paste in inventory but ceases production once 100 paste is in inventory. Increases organic polymer spoil timer by 3x