Hello,
You need to initiate the transfer from your current registrar for the domain to your friends domain registrar. Then the registrar where your friend has registered the domain will send him a mail asking for authorization for transfering the domain. Intimate your friend the same that he will be receiving the mail from the his registrar and he need to reply to that mail by giving the authority to his domain registrar to send the mail. Once the mail is send the domain transfered procedure get completed and the domain is transfered to your registrar. this is the one way to get the domain transfered in your name.
The second way is: You can create an account with your friends domain registrar and tell him to push the domain name to your account along with the ownership so that the domain is transfered with you .
Thank you.
Regards,