When you post your question, at the bottom of the page, you will see a section that says notification type. Click on that and then click on instant e-mail notification. The computer generates an e-mail when you get a reply and sends it to your inbox.
If you want to do this to a question already posted, go into your post and click on edit, then click on go advanced, then click on notification type, then click on instant e-mail notification.
It's that easy! Good luck.