National offer day is 18th April. You will get an email in the afternoon or a letter sent to you by 1st class post.
County Hall Admissions make the offers of school places to parents, not the school directly. Schools have place limits- infant classes should have no more than 30 pupils.
Once you get your offer letter, this will be followed up in a few weeks by a letter sent directly from the schools too. This will give you further information about the induction process and important dates such as visits to the schools and information meetings.
If you do not get a place offered then you can appeal. County Hall Admissions can help you - read more information via their web page.