When you’re ready to start, ideally when the weather is warmer, most nurseries would recommend starting the process at home in familiar surroundings maybe for the weekend
Please let the nursery know you are going to start prior to the training so it can be planned ahead. Take in lots of spare clothes and the nursery will continue the routine.
As tempting as it is please try not to put a nappy on because this can cause confusion and it may take longer to train in the long run.
(Pull ups may be okay at bedtime because they can be pulled up and down. However it isn’t recommended in the long term)