In most cases this is not a problem, only in circumstances where the event organiser has specified that the name on the ticket should match the ticket holder will this be relevant. Be sure to consult the event page to see if the organiser has made any specifications regarding names on tickets, and whether or not IDs will be required at the door - you should contact the event organiser directly if you are in any doubt at all.
If it is indeed the case that your friend's name needs to appear on the ticket, then click here to transfer the ticket to your friend or contact our customer support at support@billetto.com.