Here's a youtube clip if it isn't helpful look at others but a visual and verbal explanation would be good! do not wear glasses they will break in the first tackle, i used to wear them and only play football and they would fall down sometimes, get contacts i have them and even for everyday they are amazing if your sight isn't terrible just play without them you don't need to read or anything as long as you can see the oncoming player and the ball being thrown at your face i'm sure you will be fine! good luck!
Not sure about the rules, but if you wear glasses, you might want to get contacts or the special sports glasses with extra strong frames and an elastic head band (regular glasses will probably not survive one game).