Up at the top right of the web page (only when you're online) a new "tab" will appear right beside your profile link tab, and it will say "new!" and click on that, it should direct you to the answer, comment, or thumbs up. When you aren't online you can to the My Q&A link, then through there, some of the questions you answered, if someone commented on it, it should say above it that they commented. I hope this was of help to you.
Welcome to Ask! There is a little notification box that pops up highlighted in orange in the upper right hand corner of the screen. You can also go the the My Q&A tab to see if you have answers or comments there.