When you buy Bitcoin through Xcoins you will need to input a wallet address. This is your public key, which transaction can be sent to. We will ask you for this when you buy, so that we can send you your Bitcoin. You can create your Bitcoin address for free at: https://blockchain.info/wallet/, or create a wallet using a cold wallet (e.g. Trezor, Ledger) or hot wallet provider (e.g. Exodus).