I know it can feel really intimidating and scary going on your own, but there's really nothing to worry about. A lot of people go to the gym on their own and, ime, no one gives a **** what anyone else is doing so you don't need to think that people will look at you or anything.
You said you want to "tone up", does this mean you want to use weights? If so I'd advise looking at the fitness forum here so you can work out how to lift without injuring yourself with poor form.