Potty training advice?

We’ve been trying to potty train my three year old daughter for the last 4 days in time for nursery in September she still hasn’t went once in the potty we bring her every 20/30 minutes and occasionally will ask to go to the toilet where we’ll sit for 10/20 minutes and then when we come back down she then has an accident any advice on how we can get her to use the potty