There are a few ways to get a Lapras in those games:
* Trade: You can trade for a Lapras with another player.
* Catch it in the wild: Lapras can be found in the wild in various locations, like the Seafoam Islands, but it's rare.
* Events: Certain events in the games may give you a Lapras, but these are usually limited time events.
If you're playing a different Pokémon game, like Pokémon GO, the way to get a Lapras might be different. Please clarify which game you are playing.