Make metamask wallet: https://metamask.io/
Send ETH to your metamask wallet, can buy via coinbase or any other exchange
Go to Uniswap and "connect wallet": https://app.uniswap.org/#/swap
Swap for KUMA coin
Done!
Might be worth checking their reviews on Trustpilot and other sites. Loads of people saying their funds are stuck and hard to withdraw, among other issues.