Potty Training before pre-school !!!! Help!!!

[monkey362]

My little girl turns 2 in March (currently 20 months) and I am keen for her to start pre-school for a couple of mornings a week as she loves playing with other children. I have been to look around a couple of places but most say that they ask that the child is toilet trained. I dont want to rush her as at the moment when I put her on the potty she screams although she does tell me when she wants a poo. How soon did you start with your little ones and what is the best way to approach it? I almost feel rushed now if I want her to be able to start pre-school in March.