Hi Alba,
Don't be scared. When I first started, I was very nervous too. I had no experience what-so-ever with cars. In fact I nearly didnt turn up for my first practical lesson. But I forced myself to go .... told the instructor I know nuts about cars. Luckily he was rather nice and patient with me. He intro the parts to the car - what is what and then he let me have the feel of moving forward slowly, and then reversing. Don't worry too much, the instructors are trained to teach and they will know what to do. Like what was mentioned before, the cars all got brakes at the passenger side so that the instructor can brake the car in case of anything.
Please don't be disheartened with what people says coz if you think you can do it, you will be able to do it. I too was rather disheartened after my second lesson coz the instructor then (I got different instructors each time coz went thru driving school), was rather harsh when I couldn't drive properly. But I kept trying and trying, and in the end, all turned out well.
I passed on my first try and now am driving my dream car.

All the best to you. Hope you will get your license soon ....