Dealing with an unhelpful and unresponsive thesis advisor?
Ideally, you should make an appointment and meet in person with your advisor. If this is not practical you could send an email to propose a skype meeting or a phone call. 

If they don't answer your emails, wait at least a few days and preferably a full week before sending a reminder. If there's really no answer after a couple weeks and the matter is urgent, then try to call them directly in their office (during office hours).