To stake Cardano (ADA), you need to install a Cardano Wallet first. A Cardano Wallet is software that is secured by several passwords and recovery sentences and enables the Cardano owner to “store” their ADA outside of cryptocurrency exchanges.
Once the wallet is installed, you buy ADA at an Exchange such as Binanace, Coinbase or Kraken and transfer it to you wallet.
Once the ADA is in your wallet, you can choose to delegate (Stake) it to a Stake Pool. We of course suggest using CAPEX or CAPEY