In order to send Bitcoins, open the Bitcoin client and click the “Send Coins” button.
Next to “Pay To:” enter the Bitcoin address of the person you want to send it to. You’ll probably want to copy-paste the Bitcoin address because they are very long and you might make a mistake writing all the characters one at a time.
Below insert the amount of BTC you want to send.
Finally, click “Send”.
The transfers usually take less than 10 – 15 minutes to be done and confirmed, but sometimes it might take up to an hour to be confirmed, just remember you don’t pay any transaction fees and be patient.