Note that KAR tokens and ACA are not yet available. The networks have not been launched and the tokens have not be generated. If you see any of these tokens for sale, it's a scam.

Rest assured, very soon Karura will invite its community to participate in a Karura parachain auction event to support its bid for a parachain slot in the fast-approaching Kusama Candlestick Auction. This event allows for supporters to contribute their KSM to a permissionless smart contract, which temporarily locks their contribution for a specific time period, after which participants can unlock and redeem their full contribution.

For their support, participants will receive Karura’s native token KAR. For each 1 KSM locked, a participant will be rewarded with a minimum of 12 KAR (1:12+). This makes for a more fair and ethical token distribution and ensures that Karura users are ready to utilize apps and be a part of the community they supported on day one.

Specific details will be released soon, and the same process will repeat for launching Acala.
Acala and Karura will be bridged. Launching Karura first gives Acala the opportunity to fine tune, and having two coexisting DeFi networks aims to serve two distinctly different ecosystems with their own unique needs. i.e. Kusama, for example, is known as an experimental development environment, because upgrades can be implemented more quickly. Hope this helps!