You need a wallet to use a cryptocurrency. This is a piece of software that you have to install on one of your devices like your smartphone. The wallet manages your public and private keys that are used for transaction and is therefore like a physical wallet.
There are many variations of wallets with different features and security options. You have to choose which one to use based on the use case. Mobile wallets for smartphones are very popular because they can scan QR-Codes for transactions with the camera. For high amounts of coins it is recommended to store them safely in a hardware wallet.