The only thing you need to use KUMA is a wallet compatible with Ethereum.
While initializing a wallet, make sure to properly set up and back up your recovery mechanism (such as the seed phrase).
With a wallet secured, you have everything you need to interact with KUMA and any other decentralized finance services. If you are not familiar with Ethereum (or other chains) on how to handle transaction and gas costs, feel free to check Managing transaction on Ethereum.
Once you've done everything you need to do for Metamask or Rabby, just click "connect wallet" and you can use the protocol on Ethereum network.