As a self-employed childminder, you can register for tax with Revenue as a sole trader online here or you can download or request a TR1 form at your local welfare office and post it in if you prefer. You are not liable for VAT, unless your turnover exceeds €80,000 per annum.
You are allowed to run a childminding business in your home under local planning laws. It is exempt business development, once you mind no more than 6 children, so you need no change of use planning. Learn more here.
Once you are registered as self-employed with Revenue, you may be eligible to claim the Childcare Services Tax Relief.
You will also be eligible for a Childminders' Development Grant of €1,000 which you can apply for every two years.