How do I track internet use. I had teenagers stay two weeks ago and I think they visted inappropriate sites

Did you check the brower? Sites visited on my computer are listed and I periodically delete them.

Do you mean the drop down menu?

Depending on the browser you're using, you will have a History menu item. Go to the day when the teens were there and examine the history. Of course, if they're internet savvy, they'll have cleared the history and you'll find nothing. :)