Escrow service ensures guarantee and protection. Wait for the seller to acknowledge your message. On the next page, simply enter the amount of Bitcoins you wish to purchase, choose your payment method and select where you wish the BTC to be deposited. Note that the payments are processed via Simplex, and hence it requires extensive verification. I just used my credit card to send the amount to his bank directly. Next Read: How to buy bitcoin with PayPal. Leaving your Bitcoins on an exchange no matter how secure and reputed is the worst possible Bitcoin strategy you can ever have.