Your age is irrelavent, you know something they do not, so in this respect you are superior. You must not fixate on age. Yes they have more life experience, but your the one who speaks English, not them. You are the one teaching them, so your age is not the issue, i's your confidence that is. Clearly you do not feel up to the task, or worthy to teach them. That is your real problem. Maybe you are not, you are young, maybe too young to be a teacher. However you chose this job, so best do your research.

Look, you need confidence, first and foremost. I am not going to get into telling you how to teach them, that is something you should already know, or you should learn about. Do research online, look for methods of teaching ESL, use google for goodness sake.