All of the information and resources you require can be found at the Big Butterfly Count website.
If you are not in the United Kingdom, why not carry out your own butterfly survey. Spending fifteen minutes in your garden or local green space counting butterflies can never be a waste of time. Consider it therapeutic mindful relaxation.
What? You want to take part in more citizen science? If you are driving off on your holidays in the UK why not take part in the Mammals on Roads survey? Details here.