how do I turn my mute off on my itouch when I use facetime

I used Facetime with my daughter, I could hear her but she couldn't hear me. The microphone on the screen had a slash through it like it was muted. I tried to click that to unmute it. I have no clue how to get it to unmute. I went in the settings to see if I could fix it. I have no idea how to unmute it. Thanks😕